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