Immune to CC
Jax - seems to be immune to Warwick's fear while jumping or blocking. I'm not certain of the exact circumstances, but he completely ignores the fear most of the time during a fight.
Aatrox - can still use his abilities during stun, which makes stun all but useless against him. The issue with Jax is a little hard to pin down, but Aatrox ignoring stun is a very serious issue and it was absolutely clear what was happening. After the stubbornness with which the devs stood behind this uninspired Aatrox rework, how could such a blatant exploit be overlooked?