Full list of all 20 Tentacles achievements worth 200 gamerscore. It takes around 8-10 hours to unlock all of the achievements on Windows Phone.
Complete a level without taking any damage
Kill Mama Amygdala
Defeat Papa Cerebellum
Complete a "No Damage" challenge
Kill the King of the spleen
Eat 5 eyes super fast!
Take over the prefrontal cortex
Collect all pickups in the game
Rip out an eye
Get 3 stars on all levels
Defeat the Queen of the Colon
Kill a Turtlepoodle
Complete a time challenge
Escape Dr. Phluff's acid attack
Take over the duodenum
Complete the game
Complete all challenges
Complete all levels without dying
Make a perfect run
Complete a level without collecting any pickups at all