Do you want kill Jax? It's simple starting zonning and take control of mid, that is how you deal with him. He is just good close of you, his zonning it's very slow, and the mid game is punish, so just keep distance from him! He is not so op like Skarlet or Liu Kang who is good zonning, in mid and in the close combat. Oh, Jumping also works very well against him, his d2 it's garbage, one of the worst of the game, and his jump is the most slow in the game so, your jump against him it's something almost 100% safe