Booker doesn't seem to regret his actions until he realises that Andy is now mortal, and those regrets seems to focus purely around Andy. Even in the lab, he pretty much blames Joe and Nicky for having each other.
When Quynh finds him, her lust for revenge against the people who she sees as abandoning her feeds Booker's darkness that focuses on Joe and Nicky having an easier time with their immortality because they're together.
Booker's always found Nicky attractive, and it's easy enough for him to persuade Quynh that the best way to torture the entire team is to take Nicky from them.
They manage to take Nicky from the team and focus their anger on him. Torture, with a sexual component, including rape. (Maybe Quynh drowns Nicky while Booker is raping him.)
How do the rest of the team get him back? How much carnage does Joe leave in his wake in recovering Nicky.
Dark!Booker all the way; he's not coming back from this one.
Booker/Quynh/Nicky, Non-Con, Torture
When Quynh finds him, her lust for revenge against the people who she sees as abandoning her feeds Booker's darkness that focuses on Joe and Nicky having an easier time with their immortality because they're together.
Booker's always found Nicky attractive, and it's easy enough for him to persuade Quynh that the best way to torture the entire team is to take Nicky from them.
They manage to take Nicky from the team and focus their anger on him. Torture, with a sexual component, including rape. (Maybe Quynh drowns Nicky while Booker is raping him.)
How do the rest of the team get him back? How much carnage does Joe leave in his wake in recovering Nicky.
Dark!Booker all the way; he's not coming back from this one.