When people see or hear that someone defeated a Halo campaign on legendary, they usually get a chill when they think about playing it themselves. For those of you that play normal difficulty (or less) on the campaign regularly, but are looking to take on the challenge of the legendary difficulty (or looking for that Mark VI armor you get for beating the game on legendary) you might be looking for some help on how to beat it in the latest installment of the Halo franchise.
In Halo 4, the legendary campaign is probably one of the easier campaigns in the series that you will see in terms of enemy AI. While playing it on legendary does require some skill, it seems that this campaign requires more patience and strategy than skill. The difficult part seems to come with the amount of ammo you get (or lack thereof) throughout the game and the sheer amount of enemies you face at one time. Here are some tips that will help you get through the game:
Go for the easy kill first - The small minions (grunts, jackals, and crawlers) may not pack a big punch in the easier difficulties, but in legendary a single grunt with a Plasma Pistol can take you out if you don't pay attention. If a single grunt can kill you easily, it may feel overwhelming due to the fact that there will be a lot of the same enemies running around the map at any given encounter. My first tip is to take these guys out before bothering with an elite or promethean knight because they are the easiest to kill. If you have a rifle, the small minions much are easier to kill with a headshot and once they are cleared out will give you a one-on-one battle with the elite or promethean knight.
Conservation is key - Make sure every shot you take counts because ammo will sometimes be a problem and it will be at crucial points where you wish you had more. Conserving ammo means using your good weapons when you can get an easy kill or if you know there is an ammo crate nearby you can stock up on more ammo. If you want to kill something but don't want to use your current gun, pick up another in an ammo crate or on the ground and use that but don't forget where you left your good gun.
Scavenger Hunt - This tip is somewhat on the same lines as the previous tip but keep in mind that the more enemies you kill, the more ammunition there is on the ground for you to pick up. If you're low on ammo, be sure to look around for a gun to use or more ammo you can pick up.
Study their movements - As I said before, the AI isn't as smart as in Halo Reach. Previously you would not be able to predict where an elite would go if you died during the mission, and luckily (as far as making it easier is concerned) that is no longer the case in Halo 4. Make sure you study where they go if you die because you can then use that to your advantage to find the correct kill order to allow you to progress where you previously failed.
An oldie but a goodie - Most veteran Halo players will know this tip but if anyone new is reading this, here is a valuable tip for the campaign and for multiplayer. Holding the trigger for a few seconds to charge the Plasma Pistol and then releasing the trigger will send out a blast that will take out the shield of an elite or a promethean knight allowing you to go in for a headshot with a rifle. It's one of the fastest ways to eliminate tough enemies. This tactic also applies to fellow Spartans in multiplayer, so if you have the combo be sure to keep this tip in mind for a quick kill. Be careful not to hold the charge too long because it will drain all of the energy in the Plasma Pistol.
Ghost in a machine - There are a few missions that give you a ghost to use against enemies on the ground. Extreme caution is advised when using the ghost because it is a lot more fragile than it used to be. It's very easy to die while using a ghost because it doesn't take many shots to blow it up and you are more of an open target than you are in a Warthog.
Armor ability ranks - Having the right abilities makes a big difference when the odds are stacked against you. Here is a list of the armor abilities you should use while progressing through the campaign.
Autosentry - If you see this armor ability make sure you pick it up because it is the best armor ability to use during the campaign. The first reason is that it obviously does do extra damage to whomever it is targeting, but the second reason is that it provides a distraction so that you can move in closer or focus on a tougher enemy while everyone focus fires on your sentry. This will help you use less ammo on elites and promethean knights considerably because it chips away at their shields and what used to require a full clip to take down will take half of a clip thanks to the help of the sentry.
Hardlight Shield - This should be your second choice of armor abilities when you haven't come across an Autosentry because this will get you out of a jam when you're stuck out in the open with no shield left and no cover to quickly get to.
The rest of the armor abilities are not as important but can help in very limited situations so they are not even worth mentioning, but use them to your advantage whenever you can. For example, using the Jet Pack to get to the top level of a platform versus having to walk and kill your way up will make it easier for you to get to your objective.
Gun ranks - Knowing what guns to use will help make your time easier in the campaign, so here is a list of the best guns to use.
Carbine Rifle, DMR, Battle Rifle, Light Rifle - The weapon of choice for the campaign and for multiplayer. The best use for these weapons are to first take down all the grunts, jackals, and crawlers with headshots. The jackals with shields require 2 shots (one for their hand so they move the shield, and one for the head) but it is still easier to kill them this way than any other. These weapons can be used to kill elites and promethean knights as well, but make sure you get headshots on them. The promethean knights will take slightly more than a full clip to get them down while elites take about four or five shots to take down.
Plasma Pistol - The perfect partner to the previous guns. With the charged shot, this will allow you to take down a promethean knight's or an elite's shield followed up by a rifle with a headshot. Since there will be a lot of grunts laying around dead, you won't have any trouble finding these guns on the ground.
Magnum - While you only get a small amount of bullets with this gun, it's powerful enough to take anyone down with a headshot that doesn't have a shield. You won't be able to use this gun a whole lot because there is a shortage of ammo for it, but starting out a mission is generally when you can obtain this gun. Conserving your power weapon and using the Magnum to clear out the first few rounds of grunts, jackals, or crawlers and then grabbing a Plasma Pistol or similar weapon when you run out is often the best strategy.
Suppressor, Storm Rifle - This I initially ranked lower, but the abundance of ammo and guns you will see make it more useful because if you want to conserve ammo but also be able to take down enemies, this will be your go-to gun. It doesn't do a lot of damage at medium to long range but closer up you will have better luck. Make sure that you use short bursts while shooting instead of just holding down the trigger (unless you are in point blank range) because this will get them down quicker and save ammo.
Needler - This gun is great for when you're low on ammo and need to kill an elite or promethean knight quickly to move forward. If you killed all the grunts and jackals first, there will definitely be one or two laying around and just about half a clip can eliminate any shielded enemy quickly. The problem with this weapon is there just isn't enough ammo to keep it around long term, so use it if you want to conserve ammo but don't take it with you when you move on.
Sniper Rifle, Binary Rifle, Beam Rifle - Very powerful weapons but somewhat limited in ammo depending on the mission you are on. Promethean knights take at least 2 headshots to take down so keep that in mind when firing.
Fuel Rod Cannon, Incineration Cannon - These guns are very powerful but limited in ammo. If you see one, use it on some tougher enemies and then dump it for another gun.
Scattershot, Shotgun - I only found these guns useful in the last 2 missions because they allowed for close quarter combat versus the previous missions that were more open and didn't allow you to get close without getting killed. These are obviously good for close range so I wouldn't use them unless you have an Active Camo to use or are in a close quarter area.
These are just a handful of tips that I gathered through my experience playing on legendary. If you have any extra tips that could help your fellow gamers please leave them in the comments.