I think he feels a lot of anger towards his father who treated him very badly as a child.

anger 是名词，意思是"愤怒、怒气"，指强烈的不满或敌对情绪。这个词来自古英语，与德语中的"Angst"（焦虑）同源，但现代英语中专指愤怒的情绪。