Avoid attacking him when he turns on his Counter Strike.
Try to do short trades against a Jax, as Jax excels in long extended trades because of his passive and ultimate.
Be careful for every 3rd AA hit + empower in the same hit after 6.
You wanna win before 6, after 6 is where jax gets most of his power.
Late-game, Jax can 1×1 almost any champion on the game, sometimes even 1×2. Try to avoid engaging him alone. If you are a squishy character, don’t even try to kill Jax unless you are protected by a bruiser or tank, especially if you are auto-attack based.