Colm O'Driscoll was a long-time infamous outlaw operating across the Old West. In his earlier days, he had a loose partnership with Dutch van der Linde, a fellow infamous outlaw. The two would go on to found gangs named after them, the O'Driscoll Boys and the Van der Linde gang respectively.
Their odd friendship eventually turned into bitter enmity when Dutch killed Colm's brother. In retaliation, Colm murdered a woman called Annabelle, who was Dutch’s lover. Ever since these events, Colm’s and Dutch's gangs were involved in a blood feud.
Over the following years, Colm would expand his operations considerably, turning his gang into one of the largest and most powerful criminal organisations in the Old West. He was arrested and convicted for murder twice, but managed to escape on both occasions before he could be hanged.
Events of Red Dead Redemption 2
Colm is discovered to be planning a robbery of a train owned by Leviticus Cornwall. He is seen berating Kieran in the O'Driscoll camp in the mountains. He leaves the camp shortly before the Van der Linde gang wipes it out and rob the train for themselves.
Clemens Point chapter
Pearson comes to Dutch and informs him that the O'Driscoll gang is amenable to a truce and that Colm has decided to meet with Dutch to parley, but this turns out to be a ploy to capture Arthur Morgan. Colm later confronts the imprisoned Arthur, explaining that he made a deal with the Pinkertons. He is counting on Dutch to launch a rescue mission, upon which the trap will be sprung and the Van der Linde gang arrested. His plans, however, are foiled when Arthur manages to escape.
Beaver Hollow chapter
Colm is arrested by the authorities and is sentenced to be hanged in Saint Denis. Dutch, eager to watch him die, personally attends Colm's execution disguised as a police officer, while bringing Arthur and Sadie Adler with him, who are also disguised. The three immediately spot Colm’s men, who Dutch and Arthur follow. Arthur then dispatches the saboteurs, foiling the rescue attempt. Colm, initially cocky that his gang would save him, realised that his escape plan had been ruined, and began panicking before he was finally hanged.
From the little in-game dialogue and references to him he is said to be a very mean, cynic person who doesn't care about the members of his gang or really anyone else. For example when he is talking with Dutch about his brother that he "didn't really like him that much" and yet, he still murdered Annabelle. According to Kieran, "When he talks to you nicely, it's like the sun is shining and when he's mad at you, it's like the devil is upon you", which ferments his cynical demeaner to even his own gang. He is also shown to have glimpses of intelligence, like when he captures Arthur Morgan, knowing Dutch would come to his rescue, all as a ploy to capture Dutch and turn him in and then have his gang leave afterwards.
AppearanceColm is shown as an older man with long grey hair, wrinkles and gritty stubble on his face. In his few appearances he is usually seen sporting some form of green clothing. He also wears a short brimmed hat with a snake skin band.