Chad/'Numbuh 274' of Codename: Kids Next Door.
In earlier seasons, he was a cocky and arrogent, yet heroic and provably clever hero that's essentially worshiped by a good amount of the KND, yeah that's actually fine, if perhaps Mary Sue-ish.
Later season, Chad betrays the KND and tried (though failed) to hurl Moonbase into the sun, ueah, probubly fair enough, if you're gonna have him devert to the bad side, the given fact he's told he has to be decommissioned after reaching 13 prompting him to betray the KND might be decent enough motive to give a newly formed villian.
But here's where Chad irks me so much that if I ever met they guy in real life, I wouldn't hesitate to punch him in the stomach repeatingly and hand him over to the KND regardless if what he tries to say to me;
In Op: TREATY, he starts trying to kill Nigel 1 moment, then pleads his innocence, saying he was helping the KND all along, despite several episodes showing the contrary. And he claims he tried to hurl Moonbase to the sun so he could stop Cree from doing so.
Really, Chad? what made you think hurling Moonbase into the sun yourself as a more suitable alternative then, say, warning the KND what Cree was going to do, or even stopping Cree yourself?
And how the heck were you actually helping the KND? you not only tried to hurl Moonbase into the sun, but you tried to hurl a highly explosive 'Footbomb' at it, how do you explain that? And how do you explain disguising yourself as Numbuh 86's mom while distracting her long enough for the Teen Ninjas to steal the KND code module, try explaining that as well!
Any of you in this forum can say what you will about Chad, but he's perhaps the most definitive example of character inconsistancy I've ever seen in published media, and possibly a canon-made Mary Sue if I ever saw one.