Here is the full list of all 18 Capsized achievements. It takes around 10-12 hours to unlock all of the achievements on Windows.
Kill 50 enemies
Beat a level without dying
Find a secret area
Get 10 stars on one level
Win 5 deathmatches with Bots
Get at least 4000 points in Survival arcade mode
Get at least 20 stars in the campaign
Get at least 40 stars in the campaign
Get at least 60 stars in the campaign
Get at least 100 stars in the campaign
Find all secrets in the campaign
Finish a duel match with a local player
Beat every level without dying
Complete a level in COOP
Complete all levels in COOP
Kill all enemies in 5 levels
Complete 5 levels without firing a shot
Complete a level in the Armless arcade mode