Call of Duty: Modern Warfare 2

This is a trophy you're guaranteed to get as you play the game. Juggernauts are huge heavily armoured men and it takes many many shots to kill them. The first time you will encounter a juggernaut is during the spec op mission 'Snatch and Grab', at the start of the mission one runs towards you (you know this is happening because the music changes to drums). As you have an Intervention, just keep sniping him in the head and he will eventually die. Once you've killed him, the trophy will pop soon after. There's other missions with juggernauts in them such as the last two. Video by Nextgentactics:

https://www.youtube.com/watch?v=130F_ew1t6Y