It's true; supervillains are very much teenagers, in the sense that they tend to have emotionally immature worldviews and unrealistic expectations. Good people spend their immature years learning to control themselves.
A lot of "evil" happens because people are stupid and weak, but while I can (and do) pity many people who do evil, if we're going to use a simple binary good-evil metric, then Horatio falls firmly on the evil side. Granted, it seems like he had a crappy parent who didn't do much to help him along, someone who viewed him more as a science experiment than someone to nurture and raise. Everyone who turns out bad has reasons for it; I can empathize without excusing.