I'm not sure we actually have seen his upper bound to be honest. As far as I know, putting Q in wouldn't be much different from putting in Cthulu Mythos Gods or Wilhelm from Xenosaga. If someone can actually quote specific upper limits to his powers I'd be fine with it, but the only limit I know of personally is other Qs.
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From his looks Magus is Macho Man Randy Savage as an anime zombie. The black wind howls, and one of you will snap into a Slim Jim ooh yeeeah! -sonicblastpunch