This is a good question.
Okay, so I'm going to try to bring up people that no one has mentioned yet.
: She might not count as human, but she might. Iceborn have no extra resiliences or healing powers, but they do have powerful ice magic. So theoretically, if Jhin put a bullet in her head she'd die without question, but she also has the ability to track cold, and therefore heat, as if by radar. It's very difficult to sneak up on an Iceborn. Her ice magic would also mean that she can keep her opponent at a distance, and you can obviously block bullets with thick enough ice. Again, she might not even count as human, but still.
: Time travel, man.
: LeBlanc is not a real person. The name LeBlanc is a title that's been passed down forever within the Black Rose. I'm pretty sure LeBlanc that has the memories of all past LeBlancs, making her virtually immortal.
: Does he count? He theoretically can channel the full force of the Void (if it makes him), so yeah, undoubtedly powerful.
: Shen's whole job is dealing with otherworldly biz, the stuff a normal guy can't take care of.
"Shen suddenly appeared in the central court of Noxus. …Onlookers watched in rapt horror as he appeared to fight a terrible battle against a threat they could not see… …Shen seemed to flash in and out of existence, wounds blossoming all over his body from nowhere… …he singlehandedly defended [the Noxian] empire from an incursion by the spirit world." Yeah, Shen should be on this list.
: He's been touched by Aatrox, so he's possibly undefeatable in battle.
: Basically the same as Tryndamere, but minus the Aatrox.
: Time travel, man.
: Just because. He's a smart guy when it comes to killing things. He's also not reliant on his gun, he know how to use blades well and he know chi techniques invented by his father that could probably rival wuju techniques (Master Yi).



: They all have powerful magic and near mastery of combat due to their connection with godlike beings. Not even just "near mastery" with Pantheon. They can still be killed by normal means, so they count. Y'know, Pantheon could probably beat up the other three.
Others that I didn't mention because there are arguments for them here already (that I agree with):
,
,
, and
.
Btw, I don't think
counts. Also, no yordles or Jax.