Here is the full list of all 20 Thunder Wolves achievements.
Purge the island of the dead.
Destroy 1,000 buildings.
Complete a (non-tutorial) mission in 8 minutes or less.
Score at least 500,000 points in a single mission.
Kill two enemy vehicles with one rocket.
Complete the first main mission objective.
Find and eliminate Pedro in all locations.
Kill 100 enemy helicopters.
Complete a mission in co-op mode.
Complete the 'Stomp The Snake' mission on expert difficulty level in co-op mode.
Complete a (non-tutorial) mission using only rockets.
Complete a (non-tutorial) mission using only the machine gun.
Destroy your chopper with your own guided rocket.
Collect all 25 crates hidden in various locations.
Kill 10 vehicles by smashing into them.
Kill a boss/miniboss by smashing into it.
Locate and winch up the Lost Ark.
Complete at least one mission with each helicopter.
Complete all levels at least on normal difficulty.
Get all stars in all missions.