Oscar "Butch" Bowers was the abusive father of Henry Bowers.
He raised his son in an environment of racism and fear, rewarding Henry for aggressive acts against the Hanlons, a local black family. Butch himself would also antagonize the Hanlons, killing their chickens and defacing their property with Nazi symbols. It is only when Will Hanlon threaten his life with a rifle that he stops.
Being not only an abusive father, but also an abusive spouse, he also beat his wife, who left him in 1956.
After a gradual declination in Henry's mental state, both in part due to Butch's abuse, and also due to IT's influence over him, he eventually kills his father, a crime Henry was later found guilty of having committed.