EvenDavid during his "bad seed" phase? He was a pretty spooky little mansion rat and potential little murderer himself ya know.
David was a messed up kid at the beginning no doubt, Roger hadn't been the loving father that he grew to be.
Come to think of it most of the Collinses seemed to be capable of violence:
[spoiler]Roger killed a man in a drunken state (letting Burke take the blame), Elizabeth attacked Paul with a poker (believing she killed him which she did not), Judith walled up Trask in revenge for his trying to drive her insane and committing her, Quentin was physically abusive in the beginning (particularly Magda) and wounded up strangling Jenny,
Millicent tried to kill Nathan with a knife after learning Suki was his wife rather than his sister, Gabriel murdered Randall Drew and wife Edith in cold blood, etc.[/spoiler]
If I went into ALL of Barnabas' murders or violence (whether he was good or evil) I'd be here non-stop for a few days!