Trivia: At the end of the film you see two gravestones, "Priest" Vallon and William Cutting. Behind them is a river, with a view of lower Manhattan after that. You see a bridge being built, and the city growing and changing. The two men had to have been buried in Brooklyn, rather than Manhattan for this view.
Trivia: When Jenny is at the upper-class home disguising herself as a maid to burglarize it, look at the man (the home's owner) at the head of the table during dinner. This is Martin Scorsese, the director of the film.
Answer: Well, rather obviously, Amsterdam hates him because he killed his father. I mean, wouldn't you? It hardly matters that the fight was fair and that Bill showed respect about it, Amsterdam's not exactly likely to turn round, say "oh, that's alright then" and walk away. William Cutting (or William Poole, as he was in reality) was a ruthless, vicious man, who pretty much stopped at nothing to cement his control of the area. Whether he was actually worse than many of the others is questionable, but the film is based on Amsterdam's view of things - in that view, Bill is the enemy and we're supposed to see him as such.
Tailkinker ★