Resistance 3

Replay Chapter: St. Louis, MO: Sewers
After defending Brewpub, you will follow your alleys down in to the sewer, then you will emerge inside a wide open area in the Post Office. Here a Brawler will spawn and begin attacking you, and some hybrids will show up on the second floor. It's up to your whether you want to take out the hybrids or not. They shouldn't cause too much of a hassle, but it will eat up your time, so I'd suggest leaving them.

The strategy for the Brawler is the same as before, simply shoot the parts of its armor that are glowing orange. It's best to do this on Casual, so that it dies easier, and deals less damage to you. Use all of your grenades to make him go down as quickly as possible. The Deadeye, Marksman turrets, and Atomizer will do a lot of damage as well. Once the Brawler is dead, if done in under 2 minutes, the trophy will unlock. If not, reload the chapter and try again.

If you'd prefer a visual demonstration, check out this video by tima022790.