Most character depth?

is deep enough to drown a fish

This guy is raw emotion and breaks my heart every time.

and imo.

Now let me explain my reasoning.

at first glance looks like some mindless brute who loves combat, and when playing him you can get that impression also. But the longer you play him, the more you start to hear his more introspective quotes. Quotes where you realize he's not even sure of what he is, and the moments where he has an idea he's horrified. The best part is that these come out when he's walking or out of combat, so it strengthens the idea of how battle fuels him.

is an example of a bad man trying to go good only to be brought back to bad against his will. He has a lot of Krieg vibes from Borderlands 2, where he knows he's a monster and cannot control the desire to rip apart others, so instead, he just decides to direct himself on those deserving of it. He's a runaway truck without brakes, trying to hit as few good people as possible.

is a character on a mission to find out the hero that she actually is. Her inability to recognize this can be argued as a form of denial. To accept that she's the hero means she would be greater than Orlorn, her friend and mentor. As someone who views herself as a soldier, as but a single cog in a larger unit, being better than her leader or just being someone that others look up to isn't something she can admit. She's full-on imposter syndrome with her self-esteem issues.

In character. Probably Aatrox. He simply is the most "layered", if that makes sense. Not saying he is the best character but his motivations are just more complex than most other champs.

heh

No offense but I think Jhin is one of the most overrated LoL characters. People like the edgy madman-persona (like with DCs Joker) but it's really not that deep.

I think Ahri has a lot of emotional depth from her extended lore. She's highly underrated by the larger community, dear I argue that her lore and personal conflict is forgotten by most people. Especially that most tend to dismiss her as the thot character that Riot uses to make easy money (which isn't inaccurate). Ahri has hy far the most depth out of all the Vastaya champions that's for sure.

But there are many other champions with developed depth to their lore/character (although many others who have none at all) and like Ahri, some of those champions are highly unappreciated by the community. Like Brand's lore/origins were really fleshed out, that actually justifies why he's a power hungry maniac.

This may be a surprise, but her depths are still vastly unexplored. Only a distant promise.