This achievement will need to be completed in a co-operative mode (Story, Contractions, F**cking Run). When a partner goes into Last Stand, approach them and hold to pick them up off the ground. Do this 50 times across all possible game modes to earn this achievement. This can be easily manipulated in any Interval and can be done online or split screen. Have the reviver crouch behind cover while his partner stands next to him but out in the open. Revive him every time he goes into Last Stand until you have this achievement.