Many characters get killed throughout the story of GTA IV. Still, some of them are entirely optional and you can avoid killing the majority of them if you choose to. The characters that you have the option of killing are Roman Bellic, Darko Brevic, Dwayne Forge, Kate McReary, Playbox X, Francis McReary, and Derrick McReary. Either Roman or Kate is killed towards the end of the game depending on whether you choose the Deal or Revenge option. Deal causes Roman to be killed during Mr. and Mrs. Bellic. The Revenge option seals Kate's fate. Two of the McReary brothers, Francis and Derrick, can be killed during the game. You have to shoot one of them with a sniper rifle and spare the other. Finally, the two rivals Playboy X and Dwayne Forge ask Niko to take out the other, and you have to choose which one you'd rather spare, which also ends their story arc.