God Staff Jax
For once, no need to get lost in crazy explanations, it's all in the name!
You all know Jax and you've probably all played against him when he was out of control. Once in 2 or 3 items, there's not much you can do against one of the best duellists in the game. As the character himself says, "Imagine if I had a real weapon". Well, here we get to the heart of the matter, Riot gave Jax a real weapon and not just any weapon: a divine staff.
Thanks to the divine staff, Jax's skin is super-powerful. We won't even talk about the fact that he has more than two arms on his splash art. This allows him to put an astronomical amount of self-attacks, in a very short period of time. In short, it's one of the skins you absolutely need to roll over your games.