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

Psycho (36 points): Complete the game in Rorschach mode. 
Hero (36 points): Complete the game in Nite Owl mode. 
Teamwork (36 points): Complete the game in co-op mode. 
Thief (15 points): Find all abilities and pickups in Rorschach mode. 
Detective (15 points): Find all abilities and pickups in Nite Owl mode. 
Untouchable (11 points): Go unharmed for an entire level, without restarting 
from a checkpoint. 
Turbo (11 points): Complete the game in less than 80 minutes in one session, 
without restarting from a checkpoint. 
Vigilante (8 points): Eliminate 20 bad guys in 101 seconds. 
Shield (8 points): Dodge or block 25 incoming attacks. 
Strong Arm (8 points): Knock 100 people over, by throwing other people into 
them. 
Retaliator (8 points): Perform 200 counter attacks. 
Exterminator (8 points): Perform 250 finishing moves.