Here is the full list of all 26 SPINGUN achievements.
Beat the Mega Boss
Complete ALL Bosses, WOAH.
Beat the Super Boss
Beat the Ultra Boss
Survive 2 Minutes in Endless
Beat the Beamer Zone
Complete ALL Zones, WOAH.
PEACE BROTHER
Clear ballpit in under 30 seconds
Beat the Chainer Zone
Beat the Flamer Zone
Beat the Flasher Zone
Rack up 1337 kills
Survive 30 Seconds in Endless Hardcore
Only the good ones die young...
Beat the Pulser Zone
Beat the Homer Zone
Survive 60 Seconds in Endless Cursed
Survive 60 Seconds in Endless
Brrrrr!
Beat the Sploder Zone
Beat the Spreader Zone
Wow, how creative!
Survive 30 Seconds in Endless