Dead Space 3

This achievement is bugged!!!

It only works on certain enemies. It only popped for me when feeders (skinny guys) attacked my buddy (he's spamming the A button) and when I shot it off my buddy. You first see these enemies in Chapter 9.

There are certain enemies that you will be able to get this achievement on, and certain enemies that you won't be able to get it on. For example. Any "regular" necromorph you will be able to get this on by shooting the necromorph off your ally NOTE: It takes many more shots than normal to kill 1 while he's executing. I suggest bringing in a rocket launcher or something to easily get the kill. There are however some enemies that you will be unable to get this on for Ex. Stalkers. Once they are on top of your teammate they are impossible to shoot off.

Good luck.

This might not work with certain enemies as BLUEBERRYPETE said. I managed to get it with a regular necromorph that popped out of the ground to ambush me and my partner on Tau Volantis. You just have to try out different enemies to see what works. Go into co-op mode and select a reasonable chapter depending on the type of situation which would best fit your combat style, and other suggestions like which necromorphs work for the achievement. Also use a reasonable difficulty. A difficulty too high might not give you enough time to deal the damage required to kill the attacker. A good gun will allow you to rapidly kill the attacker. Every once in a while you or your partner will get grabbed by a necromorphs in combat. The person who gets grabbed will have to tap repeatedly to escape. If they don't do this fast enough, they're killed in a death animation. This whole series of events is referred to as an execution process. When your partner gets grabbed, quickly shoot off the necromorph to kill it and save them. This will unlock the achievement.