Here is the full list of all 26 Stickman in the portal achievements.
Level K is passed
Level J is passed
Level I is passed
Level H is passed
Level G is passed
Level F is passed
Level E is passed
Level D is passed
Level C is passed
Level B is passed
Level A is passed
Level L is passed
Level M is passed
Level N is passed
Level O is passed
Level P is passed
Level Q is passed
Level R is passed
Level S is passed
Level T is passed
Level U is passed
Level V is passed
Level W is passed
Level X is passed
Level Y is passed
Level Z is passed