Champion balance realisticly

Look, I know what you're all thinking - it's a game, not meant to be realistic, etc etc etc. But there is one champion who more than any other pisses the FUCK outta me in this regard - his name is gragas.

I am sorry, there is no amount of retconning or "the league makes everyone's power equal" or anything like that that can possibly make me believe that a level 18 6 item gragas could stand a CHANCE against any other champion. I mean, literally, he is a fat guy who throws ale. Please, provide this guy with SOME sort of reason why he is so unbelievably strong