I think it is Jax. I’ve fought against almost every champion over the years playing Jax. Objectively, I can easily say that Jax is the strongest duelist. Imagine that there is only one person in front of you and it is not a champion who gets unlimited power. Unless he has an infinitely powerful rune or item, Jax wins every fight without any difficulty.
Zed clearly. Zed can be mastered at such a high level that eventually gets an answer to literally every ability in league of legends. I mean, faker what was that, is quite an obvious one.
I personally am more curios of who would be the AP zed of league of legends: Ekko or LeBonk?