Wolverine has had a painful life. That pain has come from more than just all of the many fights he's gotten in. He was turned into a weapon and he's lost nearly every person he's loved over his unnaturally long life. However, the saddest thing about Wolverine is that many of the worst things in his life came from his decisions. Wolverine has been put into some terrible situations, and that's caused him to make many dark decisions.
Source:https://www.cbr.com/wolverine-marvel-dark-choices/