Jax vs Xin is hilarious, Xin doesn't stand a chance. Jax will counter strike and Xin won't be able to do jack crap for a few seconds between the counter and the stun. Ignite Xin after the counter and hit ult, you shouldn't lost more than 50% hp at best. The ignite counters his healing ability. Jax just straight up owns Xin. For the best effect, wait until Xin uses his ability that enhances his auto attacks, pretty much make him waste it entirely.