Darko

Darko Brevic is a character in GTA IV. He makes his first, and last appearance in the mission That Special Someone. Darko is the mand that betrayed Niko and his unit, which resulted in the death of 12 troops

Confrontation With Niko
During the mission That Special Someone Niko confronts Darko at Francis International Airport after getting a call from U.L. Paper. Niko and Darko have a conversation that is both in English and Russian. Darko states that if Niko kills him, he'll be doing him a favor. The player is then given the choice to either kill or spare Darko.