Deal
Roman dies at the wedding. The final mission is A Revenger's Tragedy, ending with a confrontation against Dimitri.

Near the end, Niko chooses between Deal and Revenge. The choice is irreversible, and someone close to him dies in either case.
The ending is described below. Players who have not finished the game may wish to skip it.
Roman dies at the wedding. The final mission is A Revenger's Tragedy, ending with a confrontation against Dimitri.
Kate McReary dies at the wedding. The final mission is Out of Commission, ending with a confrontation against Jimmy Pegorino.
Both routes pay $250,000, just in different missions. Money is not a factor in the choice.
Revenge: Roman survives, Niko remains true to himself, and later games in the series suggest that this is the outcome that happened.
After One Last Thing, Jimmy Pegorino calls and offers Niko $250,000 for a heroin deal with Dimitri Rascalov—the man who betrayed him. Niko seeks advice over the phone: Roman urges him to take the deal because he believes Dimitri has changed and wants to use the money for a holiday. Kate begs him not to betray himself for money. Two icons then appear on the map: a green dollar sign for the deal and a red dagger for revenge. You choose by driving into one of them. The decision cannot be reversed unless you load an earlier save.
What it costs: You lose his cousin, the only character who saw something good in Niko throughout.
What it costs: You lose Kate. Roman survives, and later games treat this as the outcome that occurred.
The financial reward is identical in both cases: 250,000 dollars. The choice is therefore not about money, but whom you are prepared to lose.
The 2009 expansions suggest that the Revenge outcome applies. Rockstar has never called it official canon, so this is an interpretation, not confirmation.
Niko travels to Port Tudor with Phil Bell. Dimitri has had the people involved in the deal killed. Niko and Phil fight through the warehouse, catch the thief carrying the money and keep it.
Kate learns that Niko accepted the deal and does not attend the wedding. Outside the church, an assassin sent by Dimitri attacks Niko. A stray shot is fired during the struggle and kills Roman.
Little Jacob finds Dimitri's men. At an abandoned casino, Dimitri shoots Pegorino and escapes by helicopter. The chase ends on Happiness Island, where Niko kills him.
After the ending, Mallorie calls to say she is carrying Roman's child. Niko promises to look after them. Kate offers her condolences, but their relationship does not continue.
Niko betrays Pegorino and storms the Platypus—the ship on which he arrived in Liberty City. He shoots Dimitri below deck. ‘It ended where it began.’
Kate attends the wedding, and Niko tells her on the way that he wants to leave crime behind. Outside the church, however, the enraged Pegorino drives past and fires at the wedding party. He hits Kate.
Roman and Jacob find Pegorino's men. Niko drives him out of the casino, pursues him by motorbike and Annihilator helicopter, then kills him on Happiness Island.
Patrick McReary calls to say that Kate did not deserve to die. Roman announces that Mallorie is pregnant—and that if the baby is a girl, she will be named after Kate.
Choose Revenge. Roman is the only character who sees something good in Niko throughout the game—and in Deal, he pays for Niko's choice.
Choose Revenge. The Ballad of Gay Tony suggests this is the version that happened, while later games refer to Roman's taxi business as still operating.
Choose Deal. Niko does exactly what he has refused to do throughout the game and pays the highest price. The final shot shows the Statue of Happiness from behind in a storm.
Create a separate save immediately after One Last Thing. Finish one route, reload that save and play the other.
Niko accepts the deal. Roman dies at his wedding. The mission A Revenger's Tragedy follows. You lose his cousin, the only character who saw something good in Niko throughout.
Niko pursues revenge. Kate McReary dies at the wedding. The mission Out of Commission follows. You lose Kate. Roman survives, and later games treat this as the outcome that occurred.
Most players choose Revenge: Roman survives, Niko remains true to himself, and later games suggest this is the version that happened. Deal has the more dramatic helicopter chase, but it costs Roman his life.
Only by loading an earlier save. Create a separate save after One Last Thing and you can play both routes.
Yes, $250,000. Deal pays it during If the Price is Right; Revenge pays it in the final mission, Out of Commission.
In Deal, Roman Bellic dies, followed by Jimmy Pegorino and Dimitri Rascalov at the end. In Revenge, Dimitri dies, then Kate McReary, and finally Pegorino.
During the story, you also decide the fate of three other characters. The game never suggests a right answer, deliberately.