Poppy.

sion

Veigar and Nasus when super farmed.

A lot to do with gear really. If Jax is built to counter someone hes one of the kings.

I'd imagine Mordekaiser can probably do it. Either by ulting Jax directly or by having someone else ghosted before engaging.

Vayne, if she can land Condemn properly?
The typical Jax will take Flash Ignite while a proper Vayne will take Flash Cleanse.
So, Vayne must Condemn Jax away when he uses Counterstrike, and when he uses Ignite she must Cleanse.
Proceed to kite with Final Hour's stealth and Tumble, and shred him down with auto attacks, and chase him down with Night Hunter.

Any champ that can delay using autos and stun him or blind him as he uses his stun on you.

probably a full build olaf. I imagine toe to toe he would be the only one to come out on top.

That or veigar chucking a full combo in his face.

ap kayle

Poppy. But that requires a wall being nearby.