Soul Hackers 2

As the description suggests, you need to beat the final battle on hard mode. Now fortunately you can change the difficulty just before the final boss, so feel free play through on easy and then jack up the pain just before the finale. You'll know you're at the end when you get to the Bones part of the 24th Municipal Tower and the game warns you that you're approaching the point of no return.

Preparation before battle:

Obviously, the higher your level, the better. I was at level 95 (which you need for fusing every demon anyways) and on my second playthrough. In order to grind up to that point, eat any meal that ups the rate of risky encounters (there are several) and run around your favorite level. Late game, you should gain one level per two or three risky encounters.

Also, to pad your characters with some nice passive buffs, complete every character's Axis dungeons up to level 5 if you're on NG+ or up to level 4 on your first run. By the end of a second playthrough, you should also have the resources to mostly max out your COMP skills. Get everything you can and equip the best augments that match your demons' powers.

Bring a roster of demons that have all the game's elements. If you can't equip them all at once, remember your commander skills (you did buy those, right?) that let you swap demons in and out. You'll want to start out the final boss with force elements, but make absolutely sure one or two of your crew are packing almighty spells.

Final prep: right before going to the Bones, I had my crew eat the Featherlight Wonton Ramen meal which gives a boost to evasion. It's available at the Noodle Stand, Karakucho. Other meal buffs will help, but this was my choice for the battle.

Lastly, max out on healing items, mostly those that restore MP, but any and everything else you can afford.

Battle time:

The final battle is divided into three stages. For the first, the boss is vulnerable to force. In lieu of force attacks, use physical attacks. Buff if you can, but I usually got rid of those skills with my demons. Use commander skills like Shield Commander to give yourself extra time. Trust me: you'll have time for it to recharge.

Now for part 2, or as I call it: the "fun" part. The boss will spawn four clones of itself. The most detrimental are blue and purple. Blue heals and purple reflects magic. However, nothing can reflect almighty damage, so wail away with anyone that has that element and have everyone pick weak elements for the other clones just to boost your sabbath gauge. It's a war of attrition at this point, whittling down the blue and purple clones. Keep an eye on health because a decent enemy combo can wreck you.

Finally comes the third part. Keep an eye on your health religiously. If you're not sure what to do in a turn, heal or buff. The boss hits can be brutal, but not unlivable. The boss will change its elemental affinities every few turns, but like with other bosses, if you test its weaknesses early, you'll see them change later. Heal, exploit weakness, use sabbath, and then heal again.

All-in-all, I overprepared. At level 95 with the strategies above, it shouldn't be too much of a challenge.

The tl;dr: if you can beat Seth, even on Easy, this will be a cakewalk by comparison. Seth is a Madam Gingko request only available late in New Game+.

I did this on my second playthrough. This isn't really that hard, but making it super easy can be quite time consuming if you overthink it the way I did.

So here's my "Ill-Advised Guide".

At the end of my first playthrough, I spent some time grinding to level 95 (to max out my Summons) by beating up on Risky Enemies. To do so quickly, I used "Adversity Marinara" to make them show up more often and weaken them at the outset of the fight. I would travel to 24th Ward Municipal Tower and then go to the portal area in Sea Area 4F - Energy Stream Area. There's a circular space on the map right there where it's really easy to avoid lower level enemies and focus on the Riskies.

The Qigong skill (Yoshitsune lvl 42) is super handy here because I could fight one or two regular enemies in between each Risky, and essentially get back all the MP I'd spent in the Risky fight. With this setup, I was able to stay out in the field indefinitely without having to return to the Safehouse and rest every few fights.

As I leveled up, I made sure to regularly upgrade my summons. Planning this out was actually one of the more time-consuming pieces, especially since I had to remake several summons as certain higher-level skills became available.

I used this site for the "recipes" to get my "perfect summons":

https://aqiu384.github.io/megaten-fusion-tool/sh2/recipes

I tailored each summon to one or two summoners, with 3 different elemental spells, a physical or gun skill to compliment the summoners' Soul Matrix skill bonuses, and then Expert Advice for critical hit rate boost and Qigong to recoup MP on each action. Each summoner also had an S-ranked elemental augment mistique and one of the Inferno/Stormcloud/Tornado/Glacier Crystal mistiques to compliment any missing element from the "preferred" summon, which were the high-level ones with lots of resistances (Seth, Lilith, Metatron, & Okuninushi). Pretty much every Summoner could hit every enemy's weakness(es). I also kept several extra summons with Recovery skills (Eternal Prayer and/or Samerecarm) and some with support skills (Tetrakarn & Makarakarn, Debilitate, etc).

On my second playthrough, I replayed ALL the content (all requests, soul matrixes, etc). I only ate Adversity Marinara at the safehouse, and always did so in between all other events/tasks. I would run through the levels, focusing on fighting most or all of the Risky Enemies that showed up on my way to each target. I was essentially farming Aromatic Wood & Woodchips while replaying the whole story. This got me enough AGI and LUK incense to get each Summoner to a base level of 100 in those attributes with no summon or accessory equipped. This made them quite dodgy and crit-happy. I spent the rest on balancing out STR and INT for all the characters as well, but I never got those above the mid 80s. It took me some time, but eventually I got to where I could beat the level 98 Riskies in 2 or fewer turns.

My team was very hard to hit, and in turn hit very hard and rarely missed. A full roster of 18 well-balanced summons provided both high survivability for the "hard" fights and an extra wallop on Sabbaths when the stack bonuses all kicked in.

The boss battle was pretty much overkill. I steamrolled it. I probably added a good 20+ hours to my second playthrough to do so, but I always enjoy an OP end-game build.

The achievement pops as soon as the battle is over.