SWORD ART ONLINE: FATAL BULLET

You will need to go to the Co-op Counter for Online Co-op. If you choose to create your own lobby, then as the host head over to the quest counter in the lobby and select Hardcore, and then whichever you want.

(For APRIL 2019 patch notes, go to the bottom of the guide)

There are 4 quests, repeated 3 times over with different levels of difficulty.

Guardian of the Ruins 1 (Lvl 75)
Magician's Concerto 1 (Lvl 75)
Banquet of Chaos 1 (Lvl 75)
Trial of the Chosen One 1 (Lvl 75)
Guardian of the Ruins 2 (Lvl 175)
Magician's Concerto 2 (Lvl 175)
Banquet of Chaos 2 (Lvl 175)
Trial of the Chosen One 2 (Lvl 175)
Guardian of the Ruins 3 (Lvl 275)
Magician's Concerto 3 (Lvl 275)
Banquet of Chaos 3 (Lvl 275)
Trial of the Chosen One 3 (Lvl 275)**

You don't need to be level 275 to beat the third bracket, however I would recommend it.

All of the missions are copy/paste of one another except for the level increase, and except for Trial of the Chosen One. Trial of the Chosen One 3 is the only one I personally struggled with.

**In Trial of the Chosen in general you will have to fight through 5 rooms before getting to the final room where you fight some of your more prominent friends. Most of the AI players will be from the Hunting Quests and do less damage and have less health. However, in each room there will be 1-2 key AI players that are tougher that you need to watch out for.

Room 1: Yamikaze (AR Assault) and Brown Butter Onigiri (Shotgun Assault)
Room 2: Dyne (AR Assault)
Room 3: Musketeer X (Sniper)
Room 4: (None, just 3 regular AI Players, but leaving the corridor is an awkward approach)
Room 5: Clarence (Tank) and Shirley (Sniper)

Final Room:

-In Trial of the Chosen One 1, you will only need to kill LLENN, Fukiziroh, M, and Pitohui, and they are only level 75

-In Trial of the Chosen One 2, at first you will need to kill LLENN, Fukiziroh, M, and Pitohui. Then a second group of friends with spawn: Zeliska, Itsuki, Kureha, and Bazalt Joe. (all level 175 of course)

-In Trial of the Chosen One 3, again you will need to kill LLENN, Fukiziroh, M, and Pitohui. Then the second group of friends Zeliska, Itsuki, Kureha, and Bazalt Joe. But now finally a third group will spawn with Kirito, Asuna, Agil, Leafa, and Sinon (all level 275)

Here is the tactical breakdown:

LLENN (will rush you with Pitohui once they become aware of you)
Fukiziroh (uses Graviton Shot and has a medium damage Grenade Launcher)
M (try to kill him first since he is a high damage Sniper and has Graviton Shot)
Pitohui (slightly more difficult to kill than LLENN)

Zeliska (healer/buffer, should be your first or second person you kill)
Itsuki (sniper/long range, keep out of his line of sight if fighting someone else, he also uses Viral Shot 4 on you, dramatically lowering your defense/offense)
Kureha (isn't the biggest threat, but don't underestimate her)
Bazalt Joe (will probably rush you as soon as the group becomes aware of you, dual wield AR DPS and has a lot of hp, so if you can ninja kill Zeliska you will probably be forced to take down Bazalt Joe after that unless you can keep him occupied with a Graviton Shot)

Kirito (extremely annoying because he always knows where you are even through Metamaterial Camouflage. He will probably have to be in your first 3 kills just to give you breathing room. Asuna, or Agil first if possible)
Asuna (group healer/buffer, generally makes life easier to take her out early)
Agil (probably the biggest threat in the entire group, his close range gatling gun does high DPS, and at long range he has a quick refresh Explosive Shot or some nonsense that does high damage. Should be your first kill, but he does have a lot of HP and armor buff. If you can't take him down early, then avoid him and stay out of his line of sight)
Leafa (low hp but high damage melee skills, so a quick kill if you can manage it and one less problem to worry about)
Sinon (not as much of a threat as Agil, but you still want to stay out of her line of sight since she is a Sniper. She plays around the the fake prediction line skill but will still shoot you if you stop moving)

I managed to beat this SOLO after a few practice runs (when I wasn't strong enough) and watching mistakes that some public randoms were making.

Here is my character build:

Personal Skills:
-Armor Break Shot 4 (INT 193 and DEX 95) This will dramatically increase the amount of damage you can do to an opponent, this will typically lost long enough to stay on an AI player in Trial of the Chosen even if you get killed and have to run back
-Power Break Shot 4 (INT 193 and DEX 95) This will dramatically decrease the amount of damage your opponents deal, this will typically lost long enough to stay on an AI player in Trial of the Chosen even if you get killed and have to run back
-Power Form 4 (STR 191 and AGI 94) This will dramatically increase the amount of damage you deal (could be anywhere from +1000 damage to doubling your damage)
-Armor Form 4 (VIT 187 and STR 93) This will dramatically decrease the amount of damage you take (could be anywhere from +1000 defense to doubling your defense)
-Healing Field Shot 2 This is a MUST HAVE because you may need to run out of sight and heal yourself as fast as possible. It is also useful if you have a boosting partner.
-Graviton Shot 4 or -Electrodynamic Stunner 4 depending on your weapon choice (heavy/light) you will need something to distract/keep away the other AI players even if its only for 2 seconds.
-and AED Shot 1 if you're boosting
-after that you can do whatever you want to add DPS or make your life easier, such as more personal buff skills, or DPS skills such as Explosive Shot 4, Blazing Shot 4, or Toxic Gas Blast 4

**WARNING: Keep in mind that if you are boosting/playing with randoms there are some things about skills that you have to balance out. For example, the new skill Skill Break Shot is BROKEN. After using it, all buffs and debuffs in the room will be removed from allies and enemies alike. I tried using it only to realize I was spending half the fight rebuffing my Power/Armor Form and having to reuse Power Break/Armor Break.
ALSO, VIRAL SHOT will OVERRIDE Power Break/Armor Break, so if a random public player is using a super weak Viral Shot 1 which is not helpful at all at level 275, it will override your Power/Armor Break Shot 4 which could cause the fight to last twice as long, or worse. Viral Shot is also ridiculous to try to level up. I think it took me somewhere between 200-400 uses to get up to level 2.

Gadgets:
-First Aid Kit 2 (from Gadget Shop, use this constantly even if you are at full health, so that if you take even a minor hit you start getting some health back right away)
-Anti-Ailment Kit 2 (from Gadget Shop, use this constantly even if you aren't debuffed, so that any debuffs automatically spend less time on you)
-Metamaterial Camouflage (from beating Death Gun/Kirito Mode, can sometimes make the AI players in Trial of the Chosen lose track of you and stop chasing you)
-Resuscitation Kit (from near the end/finishing DOTN DLC, quest reward)

Weapons I was using:

WORLD'S END++ (Attack - 3000) (green/epic/legendary rarity Gatling Gun- drops from S-Type Sniper Butterfly in White Frontier) (I got lucky with this drop, but a high LUC or accessories rare drop % should make it easier to obtain. You can also use a different weapon. )
+20% Damage vs. Humanoids (or higher)
+20% Damage vs. Mechs (or higher)
+20% Damage vs. Lifeforms (or higher)
+20% Physical Attack (or higher)
+15% Weapon Attack (or higher)
50% Overheat Buildup & Duration (or lower)
+200% Ammo Acquired (or higher)
+15% Experience points (or higher)

Peacock 4+ (Dual Wield) (Attack - 1842) (green/epic/legendary rarity Shotgun - drops from S-Type Shotgun Drones in White Frontier) (You will find this easier to obtain since Shotgun Drones are extremely easy to kill, and more abundant. A second weapon is completely optional after WORLD'S END++ because I just needed a second weapon to equip 4 more skills)
+20% Damage vs. Humanoids (or higher)
+20% Damage vs. Mechs (or higher)
+20% Damage vs. Lifeforms (or higher)
+20% Optical Attack (or higher)
+15% Weapon Attack (or higher)
+20% Weak Spot Damage (or higher)
+25% Effective Range (or higher)
+15% Experience points (or higher)

Wedding Ring (green/epic/legendary rarity hand accessory purchased from Item Shop in Lobby, also see paragraphs below)
+30 STR
+30 DEX
+30 INT
+30 AGI

Thick-Rimmed Glasses (green/epic/legendary rarity face accessory, see paragraphs below)
+30 STR
+30 VIT
+30 INT
+30 AGI

Here are my STATS:

-base STR 195 (255 with Wedding Ring/Thick-Rimmed Glasses)
-base VIT 225 (255 with Wedding Ring/Thick-Rimmed Glasses)
-base INT 195 (255 with Wedding Ring/Thick-Rimmed Glasses)
-base AGI 195 (255 with Wedding Ring/Thick-Rimmed Glasses)
-base DEX 225 (255 with Wedding Ring/Thick-Rimmed Glasses)
-base LUC 83

HP 11560
Defense 5508

**You might be asking how I got 255 with those two accessories at level 275? Yes, so here is the kicker...well, I knew I needed more VIT/AGI to get more defense mainly (LUC gives defense too but not as much). However, I also needed high STR/INT/DEX to be able to use the skills I needed. The dilemma is that level 275 doesn't give enough CP since they nerf your CP intake after level 175 to only 100 CP per level. AND they capped it so I couldn't keep leveling past 275 to get more CP.

After that, I tried to just scrape by with random public players, but as you might expect, they were horrible and actually seemed to be making things worse.

So, before you consider doing what I did with the Wedding Ring and Thick-Rimmed Glasses, know that I will be willing to help you get this done if YOU put in the work and set something up with me ahead of time. I'm not going to chase you down, drop what I'm doing, or miss my real life job for you. You will need to put in the time to ask for help.

The Wedding Ring can be purchased from the Item Shop in the Lobby. It is a green/legendary accessory. It has default stat bonuses of +1 to STR/DEX/INT/AGI. After purchasing that you will also need to complete the following quests: Home Reform (available from some random guy in the Urban District at the Shop) and Lisbeth's Handiwork (which will be available upon talking to Lisbeth in your Home after the Home Reform quest is done). Once that is done, you will have access to the Craft Accessories machine in your Home. When you use it you will want to Enhance Accessories, select the Wedding Ring, and increase the level of the stats on it. You will notice the materials required for doing this. Each stat basically requires you to farm 1-2 bosses on Extreme about 100 times each. You can decrease this timesink dramatically by visiting the Shady Material Shop in the Urban District ON EXTREME difficulty, otherwise he won't sell the rarer materials. Then you just have to pay him about a billion credits, which can be farmed by doing level 2 hardcore co-op missions by yourself to farm Emeralds, to get most of what you need. What he didn't sell were the Flight Reactors, No-Dachi Fragments, Plated Armor, and Plated Mantle, which are newer material drops from Title Updates. The stats can be raised to a MAX of +30 each.

The Thick-Rimmed Glasses are gifted to you every so often every 1,250,000 bounty gain after passing a total of 60,000,000 bounty. Bounty will be easier to farm while leveling up in White Frontier because the respawnable bosses give 75000 to 90000 bounty each time you kill them. I think I was making 3,000,000 bounty every time I grinded out about 10 levels past level 200. Once of the first Thick-Rimmed Glasses I was given gave me +10 STR/VIT/INT/AGI so I just used that one and distributed my base stats accordingly after using the Craft Accessories machine to max those out to +30 each. I could have raised my VIT/AGI past 255 for more defense, but like I said already, I needed the other stats also for skills at level 4. I received multiple pairs of Thick-Rimmed Glasses, each with varying sets of 4 stats with +10 each, so you can always hold out and farm bounty until you get the ones you want.

Since the Wedding Ring takes more materials to max out, you can always try to get a decent second pair of Thick-Rimmed Glasses, and then use the Craft Accessories machine in your Home to Transform Accessories, which will move the stats off the Thick-Rimmed Glasses onto another accessory that you can wear (beneficial since you can't wear two face accessories at the same time)

APRIL 2019 PATCH
They increased the level cap and added the weapon customization feature for Weapon Overclocking which can increase the base damage of your weapon. In all honesty after playing around with it and reading some stuff online, the base damage increases will only seem significant if you're using a high damage weapon already, like the TIamat sniper rifle for example.

For my World's End gatling gun, I used 12 overclocking chips and the damage only went up by +25-36. The average damage bonus per chip for the gatling gun is maybe 2-3 damage then. Every little bit helps, but only worth it if you are farming Makai for the Wedding Ring and Glasses upgrade parts anyway.

Another issue is that the overclocking chips only drop 2 at a time from certain bosses:
-Makai Type XX and Makai Type XXX (Demon Cave Depths, if you farm these guys make sure you use the Kureha, Pitohui, and M team and accept the Premiere's Request 2 subquest so maximize the components from farming).
-level 220 Snowstorm Queen (Meteorological Institute Depths)
-level 245 Snowstorm Ereshkegal (Meteorological Institute Depths)
-level 245 Freezing Menace (Bridge of Hope)
-level 270 Cocytus Nix (SBC Abend)

I can verify that the chips don't drop every single time. Needless to say, these bosses aren't a walk in the park either.

I was playing around with the single player a bit before I tried more of the multiplayer. I'll test out the hardcore co-op for the achievement again sometime. I am still willing to help people as before so let me know if you need help.

They also added more Hardcore Co-op quests for multiplayer, but they are NOT needed for the achievement
-Special Invitation (alpha) (Lvl 285)
-Special Invitation (beta) (Lvl 285)
-Special Invitation (gamma) (Lvl 285)
-Special Invitation (alpha) (Lvl 300)
-Special Invitation (beta) (Lvl 300)
-Special Invitation (gamma) (Lvl 300)

Let me know if the hardcore co-op seems completely different from my details above also, since they might have changed it in the patch.

As always, let me know if I missed anything or if there are any ways to improve my guides.