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.
If it’s 1v1 I’m sure no champion can beat trundle 1v1 if he actually builds for 1v1.
His W gives 110% bonus attack speed, 52% movement speed and 25% increased healing. His Q gives 40 AD and reduces the enemy AD by 20 so that’s 60 AD difference. His R makes him drain literally 30% of the targets HP and 40% of their armor and magic resist.
If he actually builds for 1v1 like (Botrk, Divine, Hydra, Steraks, Thornmail, Tabi’s) he’d destroy Jax and Fiora and I’ve seen one of my friends who mains trundle do it in front of my eyes lol.