Here is the full list of all 13 Swelter achievements.
Freedom is life not according to someone else's rules. Bet on independence.
It is easy to break one straw, but it is more difficult to break a bunch. Bet on unity.
Open all caches marked with a radio beacon.
He will not tell wisdom, but he will help find wisdom. Find a yurt with a vortigaunt.
Find the AK left many years ago.
Eliminate the missile turret.
The attacking helicopter looks best on the ground. Bring it down.
Complete the bonus part.
Tea.
Get killed by a train run at the very beginning.
Show your superiority in the air.
Rob the Combine armory.
Survive a failed train disembarkation.