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