Here is the full list of all 30 BattleBlock Theater achievements.
Get 100 kills.
Complete the first four finales in any mode.
Kill your teammate 50 times.
Die enough times and we give you a prize.
Get eaten alive.
Find a secret level.
Free a fellow prisoner.
Get yourself a cool new weapon.
Complete the story's opening sequence in any mode.
Get an A++ in 10 levels.
Get a letter grade in every level (except Encores) in Normal Solo Story Mode.
Get a letter grade in every level (except Encores) in Normal Co-op Story Mode.
Get a letter grade in every level (except Encores) in insane solo story mode.
Get a letter grade in every level (except Encores) in insane co-op story mode.
Complete all the Encores in any mode.
Collect 10 Golden Hats.
Get a letter grade in all eight finales in any mode.
Be on the winning team in 100 arena matches.
Be on the winning team in one arena match of every mode.
Free 50 prisoners in the Gift Shop.
Collect all the prisoners of one head shape.
Free all the prisoners in the Gift Shop by unlocking or trading.
Collect all the weapons in the Gift Shop by unlocking or trading.
Make a trade with someone.
Complete an encore level in Story Mode.
Play with the Behemoth or someone with this achievement in an online game.
Successfully use every melee attack move.
Use each weapon successfully.
Complete 10 user-created levels in a single Featured Story playlist.
Download and host a game of user-created levels.