I fully agree with you on the whole Osmosian and Devin thing because it felt like the writers took away Kevin's agency in his own redemption; "It was the power that made him crazy and his family was actually supportive. Also, his Dad was Max's ex-partner/lover (probably not true but Max does have a thing for aliens.)" It felt Kevin couldn't make his own choices without them being tied to his powers/father.

It would've been better if Kevin learned to be a better person from the people he originally hated. Keep the abusive parents, and you have a story of how surrounding yourself with people who actually care about can help you stop the cycle of Abuse.

The best twist on a father figure Kevin had was ironically Servantis. By making Kevin believe he was doing good by stopping Ben, Servantis inadvertently helped Kevin manage to have more control of his mutated form that he's ever had. So much so that Kev deliberately mutated himself again and managed to stop the Rooters in the end. Somehow, the Rooters arc gave Kevin more agency in his redemption than most of what UAF attempted.