Halo 5: Guardians

For "Top of the Food Chain", You must kill a legendary boss in Warzone.
(Looks like the top solution was edited to include Firefight after I posted this)

There is a NEW and EASIER way to get this achievement as of April 14th 2016: Firefight!

In Warzone Firefight, A team of 8 spartans fights through 5 rounds of AI enemies. During the course of the match there will be many legendary bosses.

A legendary boss in identified with a yellow mark next to the name of the boss (There are some elite Legendary bosses with a red mark).
The traditional way (normal Warzone) of obtaining this (which is covered well in other solutions) can be very frustrating. You must be the person to get the last hit on the legendary boss to get credit for the kill and the achievement. You would have to compete with teammates for the kill, while being targeted by the boss and other AI enemies, and the entire other team of Spartans. There would only be one legendary boss at a time, so the chances of getting the final kill will always be slim.

In Warzone Firefight, there will not be another team of Spartans trying to kill you, less teammates of your own, and since there are tons of legendary bosses... you have a much better chance of killing one. In fact, when I got my achievement, I believe that I was just lending support with the machine gun turret. Like other guides have mentioned, saving up your req points for heavy vehicles or big weapons would help take out these bosses.

*If this solution helped you in some way, please vote positively. If you think it needs improvement, please let me know how in a private message or by leaving a comment.*

For information:
White marker: Normal Boss
Yellow marker: Legendary Boss
Red marker: Mythic Boss


Before Update 8 Warzone Firefight

Escape from A.R.C:
- Baron 'Sraom ±6min
- Knight Strategos ±12min
- Warden Eternal ±18min

March on Stormbreak:
- Commander Lochagos ±1min
- Captain Wamik ±8min
- Warden Eternal ±18min

Raid on Apex 7:
- Tankmaster Rok ±8min
- Captain Hestro ±12min
- Warden Eternal ±18min

Update 2 Cartographer's Gift
Battle of Noctus:
- Pilote 'Dalamen ±6min
- Warden Eternal (first emergence) ±12min
- Warden Eternal (second emergence) ±18min

Update 5 Ghosts of Meridian
Skirmish at Darkstar:
- Endurence-of-Will ±6min
- Lord Viratus ±12min
- Warden Eternal ±18min

After Update 8 Warzone Firefight

Escape from A.R.C:
- Grunt Jockey ±6min
- Knight Praetorian ±12min
- Swarmlord Magtanggol ±18min Mythic
or
- Warden Eternal ±18min Mythic

March on Stormbreak:
- General ‘Soest ±6min
- Commander Lochagos ±12min
- Swarmlord Nakagagalit ±18min Mythic
or
- Warden Eternal ±18min Mythic

Raid on Apex 7:
- Grunt Jockey ±8min
- Knight Strategos ±12min
- Commander Sever ±18min Mythic
or
- Deacon Pipap ±18min Mythic

Update 2 Cartographer's Gift
Battle of Noctus:
- Lord Tyrik ±10min
- Lord Venrex ±10min
- Knight Sublimis ±18min Mythic
or
- Jockey Flibyam ±18min Mythic

Update 5 Ghosts of Meridian
Skirmish at Darkstar:
- Soldier Armsman ±6min
- Lord Viratus ±12min
- Endurence-of-Will ±18min Mythic
or
- Warden Eternal ±18min Mythic

Update 8 Warzone Firefight
Attack on Sanctum:
- Jul ‘Mdama ±6min
- Knight Dominarch ±12min
- Hamyap the Hammer ±18min Mythic
or
- Warden Eternal ±18min Mythic

The multiplayer AI bosses that spawn around the map are nothing to trifle with. Even the ones that are not of legendary rank (the white ones, for instance) are surrounded by minions and will kill you much easier than you can kill them. It takes many many hits for them to go down. Personally, I prefer the ones that are on the ground than in the air, since I find them easier to hit.

When a legendary boss appears on the map it will be shown by a yellow marker. If you have a Scorpion Tank req card or any other vehicle or weapon that will help you to do precise and considerable damage (Ghosts, for instance, do not), save it for this achievement.

It's important to notice that other people from your team or even the adversary might try to compete with you for the killing blow against the Legendary Boss, so that's another variable to consider and that can delay you from obtaining this achievement.

If somebody kills it or kills you before you're able to pull it off, don't worry and keep trying. This is not as hard as it may sound.

Here's a QuickGuide fer ya. I'm talking strategy here! You already know the basics, Spartan! I'm gonna tell you how you can manage the strategy of doing this.

There are 2 main ways to get this:
1. Go BIG -- get yourself some big guns, like the Fuel Rod Cannon, and do some real damage.

2. Be PERSISTENT -- all you need to do is get the last shot in. You can let someone else do the big damage, and focus on shooting when the Legendary Boss' health is low. ProTips: try to not get killed by the opposing team, take some cover and don't draw attention to yourself until it's go time. This will take a bunch of tries in most cases, took me about 6 matches, it's really luck-based but you're managing the strategy. I got the kill with the Battle Rifle.

Having struggled with this achievement for a while, I want to share my tips. This is intended to act as a supplement to the existing guides, so I won't cover that information again extensively.

1) Vehicle cards tend to be rare, especially useful ones.

Ghosts have their uses, but as noted elsewhere aren't heavy hitters.

Wraiths and banshees are good, but also make you a huge target and are vulnerable to skilled enemy players. Furthermore, the ubiquitous Warden Eternal can stun them with an attack that acts like charged plasma pistol and is difficult to doge, especially in a tank, after which he likes to tear you up with other attacks while keeping you chain stunned.

Scorpions are in many ways the best, but they are slow and also relatively easy for enemies to destroy. So before you blow a powerful vehicle card trying to kill a legendary boss, get to know where they spawn, how long it usually takes for them to go down, and how long it will take you to get there. I wasted my only scorpion card because it took me too long to drive to the boss, and it dropped from full health to death by the time I got there.

Mantises are great too, but take a lot of energy.

If you rank up to level 18 or so, you will start to get more good vehicles more often, especially if you unlock a lot of permanent stuff early on. More on that in a second.

2) Power weapons cost less energy, and many of the useful ones are less rare by far. Power weapons also make you less of a target to the enemy team than vehicles.

Hydras and SAWs in particular are fairly common (I think I have over 20 SAW cards in inventory now, and I used them a lot). They do decent damage, and the SAW in particular fires so fast, with such a huge clip, that it gives you a decent chance of getting that final shot in. I've had a few legendary boss kills now, and all of them but one were with the SAW.

All the power weapons have their uses, but rocket launchers have limited ammo and fuel rod cannons can be hard to hit with, especially against vehicles. Spartan Lasers are insanely good though, don't waste those on players. They're the best thing to use to kill the flying legendary bosses in most player's opinion.

Plasma pistols are surprisingly good too, in the right circumstances. If you chain stun Tankmaster Rok, for example, he will get out of his wraith and become much easier to kill. 1-2 charged shots will also take out any sheild. Don't bother on the flying bosses though, they will almost always dodge the emp shot.

3) If you can't seem to get good cards I have two pieces of advice: first, you won't get much that is useful until you level up some more. You can do this by playing and learning Warzone, or you can do it in Arena, your choice. Second: buy silver REQ packs with your REQ points. Get the gold achievement out of the way, certainly, but Silver packs give you just as many permanent unlocks, so buy those until they stop giving you permanents. That way you maximize the options for weapon certifications (meaning you get more usable weapon cards) and get the more common permanents out of the way. This will also get you more of the useful but not insanely rare cards, like SAWs, so that you can maximize your chances at the achievement. Then switch to gold if you want to get the rare unlocks.