Here is the full list of all 26 ASSASSINATION BOX achievements.
BUY EVERY UPGRADE FOR ONE WEAPON
GET 10,000 ASSASSINATION POINTS
GET TOTAL 1000 KILLS
BUY ANY CUSTOM PART
KILL 100 ENEMIES IN ONE GAME
GET RANK "S" FOR THE FIRST TIME
SO YOU ACTUALLY MANAGED TO RUN THE GAME
GET 100,000 ASSASSINATION POINTS
GET PROFILE LEVEL 10
GET PROFILE LEVEL 25
GET PROFILE LEVEL 50
GET PROFILE LEVEL 75
GET PROFILE LEVEL 100
GET 100 HEADSHOTS
FULLY UPGRADE HEALTH
FULLY UPGRADE AMMO
FULLY UPGRADE MOVEMENT
FULLY UPGRADE JUMP
FULLY UPGRADE SLOW TIME
FULLY UPGRADE ACTION POINTS
FULLY UPGRADE DODGE
FULLY UPGRADE GRENADES
FULLY UPGRADE MONEY
FULLY UPGRADE DASH
GET "S" RANK ON EVERY LEVEL IN SURVIVAL MODE
GET "S" RANK ON EVERY LEVEL IN TAKEOVER MODE