Halo 4 Cheats

Explore the Floor (20): Tricked or forced a Hunter to fall to his demise in mission 6.
Forerunner (10): Completed mission 3 on any difficulty.
Game Changer (5): Created and saved a Custom Game type in War Games.
Give Him the Stick (20): Took out both Hunters using only the Sticky Detonator in mission 7.
Hanging on the Combat Deck (30): Won 20 War Games matchmaking matches.
I <3 Red vs Blue (15): Won 5 War Games matchmaking matches.
I Need a Hero (40): Completed the Campaign on Heroic or harder.
Infinity (10): Completed mission 4 on any difficulty.
Knight in White Assassination (20): Assassinated a Knight in any Spartan Ops mission.
Lone Wolf Legend (90): Completed the Campaign solo on Legendary difficulty.
Midnight (10): Completed mission 8 on any difficulty.
Midnight Launch (20): Got significant air in the Warthog at midnight in mission 2.
Mortardom (20): Hijacked a Wraith and used it to kill at least four enemy Wraiths in mission 5 on Heroic or harder.
Movin' On Up (25): Ranked up your Spartan-IV to SR-20.
No Easy Way Out (20): In Ch 1, Ep 5 of Spartan Ops survived the enemy assault during the defense on Normal or harder.
No One Left Behind (20): Saved at least one Marine in Chapter 3 of Episode 2 of Spartan Ops on Heroic or harder.
Not Some Recruit Anymore (15): Ranked up your Spartan-IV to SR-5.
Operation Completion (15): Completed a Spartan Ops Mission on any difficulty.
PWND (5): Changed your Service Tag in the Spartan ID card.
Reclaimer (10): Completed mission 5 on any difficulty.
Requiem (10): Completed mission 2 on any difficulty.
Roses vs Violets (20): Found one of the RvB Easter Eggs in Spartan Ops.
Sharing is Caring (5): Uploaded a File to your File Share.
Shutdown (10): Completed mission 6 on any difficulty.
Skullduggery (15): Completed any Campaign mission with 3 or more Skulls on Heroic or harder.
Snapshot! (5): Saved a Screenshot from the Theater.
Terminus (50): Found all of the Terminals in the Campaign.
The Cartographer (5): Created and saved a Custom Map in Forge.
The Challenged (10): Completed a Challenge.
The Challenger (20): Completed 25 Challenges.
The Director (5): Saved a Film Clip from the Theater.
The Legend of 117 (70): Completed the Campaign on Legendary difficulty.
This is my Rifle, This is my Gun (20): Carried a UNSC weapon all the way through mission 3 on Heroic or harder.
Wake Up, John (20): Completed the Campaign on Normal or harder.
What a Poser! (5): Changed your Spartan's pose in the Spartan ID card.
What Power Outage? (20): Completed Chapter 4, Episode 5 of Spartan Ops without losing a generator on Heroic or harder.

Halo 4: Crimson Map Pack Achievements
Bigfoot (20): In Crimson DLC matchmaking, kill 20 enemies using the Mantis' stomp attack
Clay Pigeon (40): In Crimson DLC matchmaking, shoot an enemy who's airborne from a Man Cannon
David and Goliath (20): In Crimson DLC matchmaking, board an enemy Mantis
Now They Fly? (50): In Crimson DLC matchmaking, get a kill while airborne in a Warthog
ODST (30): In Crimson DLC matchmaking, kill a player while airborne from a Man Cannon
Pump Yer Brakes (40): In Crimson DLC matchmaking, score the killing blow on a Mantis
Size is Everything (20): In Crimson DLC matchmaking, kill 20 enemies with a detached Machine Gun Turret
Special Delivery (30): In Crimson DLC matchmaking, kill an enemy with melee when landing from a Man Cannon

Halo 4: Majestic Map Pack Achievements
Bird of Prey (50): In Majestic DLC matchmaking, perform 5 'airsassinations.'
Bullet Sponge (30): In Majestic DLC matchmaking, get the 'Close Call' medal twice during one match.
Callin' in the Big Guns (40): In Majestic DLC matchmaking, call in 3 ordnance drops during the same game.
Clever Girl (10): In Majestic DLC matchmaking, kill 5 enemies while Active Camo is active.
Didn't See It Comin' (10): In Majestic DLC matchmaking, assassinate an enemy who's in zoom mode.
Flash of Light (30): In Majestic DLC matchmaking, get a Double Kill or higher with one Pulse Grenade.
I See You! (10): In Majestic DLC matchmaking, kill 5 enemies while Promethean Vision is active.
I Thrust at Thee (20): In Majestic DLC matchmaking, perform a melee kill right after using Thrust Pack.
Last Man Grinning (20): In Majestic DLC matchmaking, get 4 kills using the SAW without dying.
Pigs Can Fly (30): In Majestic DLC matchmaking, kill 3 enemies while they are using Jet Packs

Halo 4: Castle Map Pack Achievements
Ashes to Ashes (10): In Castle DLC Matchmaking, disintegrate 6 enemies using Forerunner weapons.
Beating up the Beat (30): In Castle DLC Matchmaking, perform 5 melee kills in a single match.
Dodge This! (20): In Castle DLC Matchmaking, get two direct Spartan Laser kills in one match.
Hello Nurse! (30): In Castle DLC Matchmaking, heal a near-death teammate with Regen Field 5 times.
Outta My Way! (40): In Castle DLC Matchmaking, kill 5 enemies during a match by running them over.
Scrapyard (30): In Castle DLC Matchmaking, destroy 2 vehicles during a single game.
Sight Seeing (20): In Castle DLC Matchmaking, complete a match in any mode for each Castle map
That Won't Save You (30): In Castle DLC Matchmaking, assassinate an enemy who is using a Hardlight Shield.
What is Yours is Also Mine (40): In Castle DLC Matchmaking, disable a vehicle and then hijack it.

Legendary Completion Unlockables
After completing the Campaign on Legendary, Single Player or Co-op, you will unlock a few features to be used in Infinity.

"117" Emblem: Beat the Campaign on Legendary
Legendary Visor: Beat the Campaign on Legendary
Mark VI Armor: Beat the Campaign on Legendary