Here is the full list of all 21 Kick-Ass 2 achievements.
Find all the Wi-Fi hotspots
Cross out the 24 graffities
Finish off Chris D'Amico once and for all
Defeat Chris D'Amico's thugs
Defeat Mother Russia
Survive the battle for Manhattan
Get rid of the Tumor
Cross Central Park
Chase the Tumor through the sewers
Escape with your life from the Cemetery
Survive the clash with Mother Russia
Eliminate all the enemies in the Justice Forever Headquarters
Reach the entrance to Headquarters
Leave the subway
Defeat Genghis Carnage
Reach Genghis Carnage's whorehouse
Cross Chinatown
Defeat Black Death
Reach the Goths' Lair in the subway
Fight your way through the Goths to the subway entrance
Rescue Dr. Gravity