Key point here is that he lost decisively to the pony tail, and was wrecked by Anissa. He momentarily held his own against a relatively weak, and past her prime viltrumite, and didn't stand a chance against an elite like Anissa. @John_McMurray also makes a good point about Mark's abilities.

However, I will concede that this is a piece of pop culture, and you shouldn't have to be a big fan of the comics in order to understand why the cartoon isn't inconsistent. THAT is bad writing.