Resistance 3

The EMP grenade will be the first grenade you receive. All you need to do is play through the game until you find some Steelheads (Auger wielding Chimera), wait for them to put a shield up, and toss an EMP grenade at them, and their shield will go down. If you have more EMP grenades, you can wait for them to put up another shield and do it again. This trophy can be done at any time throughout the game, as it carries over across all playthroughs and chapter selection. Alternatively, like all combat trophies, this can be farmed at a checkpoint. The best place to do so is the chapter: Haven, OK: Run! Wait until the game first introduces the Steelheads. 2 of them will come out of a building, and likely both put up shields. Toss an EMP at them to take out both shields, then let them kill you.

Your trophy progress will be retained, and the enemies will respawn, allowing you to repeat the process until you have unlocked the trophy. The progress towards this trophy can be track through the Extras menu, under the tab for Rewards.