I can see where you’re coming from considering him a Boy Scout, but in my opinion he had a solid character arc from naive and somewhat clueless, to cynical and gritty during the loathed xindi arc, and then to seasoned mediator during the last season.

Which would then have eventually led to him becoming actively “evil” from starfleets perspective by taking on the role of future guy who commands the suliban in the past. Certainly a colorful character arc I would say.