Halo: Reach

Incredibly simple achievement.

Approach an enemy from behind, and melee kill him. (Hold RB is the default button).

If the melee hit kills him from behind, it will count as an assasination and the achievement will pop.

Best tactic is when someone runs in front of you on matchmaking, use sprint to catch him then hit him.

You can do this with a second controller.

- In the "Main Menu" select "Custom Game"
- Press Y (Network Mode) and select "My Xbox 360 Console"
- Select Game Type "Assault"
- Select a small map like "Powerhouse"
- Start the game
- Find the other player and stand behind him (you don't have to sneak up)
- Press and HOLD the melee button (RB) until the achievements shows up

At the very beginning of the "Nightfall" mission you will come upon a hapless Elite with his back to you, an easy target for assassination.

For a long time I didn't realize that you must hold RB, if you tap it it will "melee from behind" but if you hold it for just under a second it will assasinate.

Any grunt in campaign or Firefight, a friend in a custom game, matchmaking...
Nightfall has a helpless elite, though if you do the "they came to hear me beg" achievement you will pop both at once.

I can get 3 to 9 assassinations in some matchmaking games.

I got this on the 2nd mission of the campaign. When you see weak enemies (the small ones), get behind him and assassinate him by holding RB.

This achievement can be obtained anywhere on any enemy, but in the interest of a concise walkthrough through the campaign and where this achievement will unlock in said walkthrough, I've included my route for Mission 4 of the campaign below, which will net this right at the start.

Mission 4 – Nightfall

Mission starts at 0:28:59 in the walkthrough video below.

You’re definitely going to want to watch the video for this one. This mission can be cleared in five to eight minutes if you follow the speedrun route, or it can take you in excess of an hour or more if you fight your way through everything. I’d suggest doing the speedrun, as it’s quite simple, takes very little skill, and can save you tons of time. Don’t forget to assassinate the Elite at the top of the hill at the start of the mission for "That’s a Knife".



If you choose not to follow the video and make your own way, I would still suggest doing the ‘door glitch’. You’ll reach a part with a bridge you must cross with an Elite patrolling among some sleeping grunts. Just past the bridge is a forklift. Try to assassinate the Elite without waking the grunts, then drive the forklift to the door straight ahead. Align the vehicle with the driver’s side against the door at a slight angle (about 30 degrees). When you get out, you’ll pass through the door and can run to the end of the mission without fighting anything else. At mission completion, you’ll unlock the next story-related achievement for finishing it on normal or higher.

Get behind the enemy and then hold (default control setting).You can do this in many ways, stand still and wait for an enemy to pass through a door (being invisible with one of the equipment helps a lot), surprise an enemy from behind who is attacking your ally or even fly with your jetpack and land behind the your enemy.