Complex sentence: Unlike the other villains, he considers Ron Stoppable a worthy opponent rather than a clownish sidekick, since he considers Ron (and Rufus) as the only other one besides himself exposed to Mystical Monkey Power.
Split into simpler sentences: Unlike the other villains, he considers Ron Stoppable a worthy opponent rather than a clownish sidekick. He considers Ron (and Rufus) ss the only others, besides himself, exposed to Mystical Monkey Power.