Did you think defeating the Elite Four with a Magikarp was impressive? That Magikarp was level 100. At that level, you can tank through most things. This Bidoof owned by ImEpicToast is level one, and yet it manages to defeat one of Pokemon's fiercest foes, Cynthia -- who is the champion of the Elite Four in Diamond, Pearl and Platinum.
(Although this seems to be Pokemon Black's and White's Cynthia, not that that makes this any less impressive: it's level 75 Pokemon versus level one Pokemon!)
To be clear: there is cheating involved here, but it's only something that prevents the player from levelling up according to the player. Otherwise, you can see the Bidoof's stats at the end; they look legit. So how is this possible? The feat is accomplished by smart usage of the of the item leftovers along with the moves toxic, swagger, substitute, thunder wave -- all of which Bidoof can learn via TM. Bidoof doesn't even need to attack the other Pokemon directly, it can just give them status ailments and let the Pokemon hit themselves. It's an effective tactic, if not humiliating and enraging.
Level 1 Bidoof Destroys Cynthia [ImEpicToast]