Successfully complete one of the following tasks to get a trophy:

Exterminator (Bronze): Defeat the giant spider.
Unstoppable (Bronze): Finish a zone without losing a life.
Annihilator (Bronze): Kill more than 85% of the total enemies in a
zone.
Small Arms Expert (Bronze): Finish a zone without using grenades
or nukes.
Twin Medal (Bronze): Finish a zone in Co-op mode.
Speed Freak (Bronze): Finish a zone in less than 15 minutes.
Tricked Out (Bronze): Max out all of the vehicle power-ups.
Sharp Shooter (Silver): Keep your accuracy higher than 70%.
Lair Slayer (Silver): Complete all underground zones without using
a continue.
Peace Maker (Silver): Finish a zone killing less than 50% of the
enemies.
Survivor (Silver): Finish a zone killing 60% of the units on
foot.
Assault Hero (Gold): Complete the game.