Here is the full list of all 12 Castle Crashers achievements. It takes around 15-20 hours to unlock all of the achievements on Windows.
Win 40 Arena Online Matches.
Complete the Home Castle through Barbarian Boss areas without attacking any foes.
Collect all 4 princesses' kisses in a multiplayer game.
In a 4 player game, resuscitate each of your fallen comrades at least once.
Collect all the animal orbs.
Survive until 2:30 in a Back Off Barbarian match.
Defeat any boss by playing one of his own minions.
Navigate the Abandoned Mill without hitting any obstacles.
Complete the game using any character.
Defeat any end boss without using any magic.
Find and dig up ten buried items.
Using a catapult, fling a knight with maximum power.