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