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