Late game champions and early game win rates

Kind of a simple question for the community. If a champion is suppose to be a late game power house, what do you think is an acceptable early game win percentage? Yeah i know the numbers can be a bit weird since no one champion wins or losses the game by themselves, barring the champion who went 20-0 in the first 15 mins or 0-20 in roughly the same time frame. So the basic idea is what is an acceptable win rate in the first 0-25 minutes of the game, for a champion who is designed to be better the longer the game goes. Personally i would say anything above 45% is fine, while anything above 51% is too high (assuming the win rate just keeps going up as the game goes longer).