lategame vayne has the carry potential of a 6 item kog maw, without his drawbacks.
she gets to deal a shitload of damage with a ton of outplay potential in her kit, that allows her to 1v1 just because. other lategame hypercarries need dedicated peel teamcomps to work. twitch, kog maw are exactly like that.
they can shred an entire team to pieces, but while they do, they can barely move. strength and weaknesses.
there is no reason vayne is one of the best 1v1 marksmen in the game while simultaneously being able to hard carry. she doesnt have weaknesses, but only an assortment of strengths. she has tools to counterplay her opponent without having counterplay herself.
the only reason she doesnt have even more absurd pick and winrates after her buffs like at the end of season 5 right now, is because she loses a lot of matchups in lane early on. just wait for another meta shift that puts her back into the game, and her winrate is going to explode.
just like jinx. absolute cancer.