Accomplish the indicated achievement to get the corresponding number of Gamerscore points:

No Mercy (30 points): Finish all three chapters with combat rank S in story mode.
Martial Art Master (20 points): Unlock all combat moves in story mode.
Carnage (20 points): Kill 300 soldiers in story mode.
Path of Justice (20 points): Finish the game on any difficulty.
Path of Revenge (30 points): Finish the game on Veteran difficulty.
Bonus Hunter (20 points): Find and collect 36 bonus ulyssium.
Assassin (10 points): Kill 10 soldiers using stealth in story mode.
Combo Slayer (10 points): Kill 10 soldiers using combo attack in story mode.
Hollywood Star (10 points): Get spotted by security cameras at least 10 times in story mode.
Rank Captain (10 points): Kill the Prison Boss.
Rank Major (10 points): Kill the Laboratory Boss.
Rank Lieutenant Colonel (10 points): Kill the Nuclear Base Boss.