Big surprise, I'm talking about Yasuo (also Fiora and Irelia to some extent)
A marksman gets ahead and they are still super squishy, they have to take basically zero damage to survive long enough to do damage.
Yasuo gets 100% crit with 2 items and then can build bruiser shit with lifesteal, he can survive all your burst and heal back up in like 4 autos while perma dashing. Strong early game, strong late game.
I like playing around my team - this is a team game. Champs should be balanced as such. Every champ should have a weakness.