|Characters need to be human and have flaws. Characters who are presented as basically rocking in everything are caricatures, rather than fictitious people. We like people for the things we perceive as cool about them, but we fall in love with them for their flaws. Flaws fundamentally make characters relatable.|
The problem here is that flaws don't make characters relatable by themselves. Being relatable/flawed also doesn't mean that the character is automatically more interesting. In Warwick's case, being a caricature was his entire shtick, it made him interesting. he was the Big Bad wolf who got away with everything and we were polarized into liking him or hating him. Some of us liked the fact that he satisfied our urges for some badass evil character who got away with causing massive devastation and by the same token, others hated him for doing so and for bumping off Urf. He worked as a big bad caricature. Actually, now that I think about it, he's STILL a caricature except he's now one of those side-villains who ends up causing their own destruction and is thoroughly unlikeable.
Now he's just lame. As stated before, he becomes a one-dimensional cartoon villain who gets beaten up by purple smurfette. It really doesn't help that his bounty hunter lore makes him sound more like a creepy kidnapper than a badass Boba Fett type. He then goes on to screw himself up (oh yeah! He's impatient and stupidly impulsive when it comes to a mysterious potion that isn't even finished! SO relatable!)
Ultimately, this leaves us with the people who liked him before thinking he's a wimp, and the people who hated him are now laughing at him. Warwick's quest to retain his humanity holds no real significance to us on an emotional level because he's a horrible person with no redeeming qualities. We ALL know that he's never going to get Soraka's heart (lol) and will remain forever remain unredeemed for his idiocy. Even if he went as far as to go to Viktor, it either wouldn't stick, or he'd become even more lame for having to get help (and canonically turning into a robot).
There are two solutions to this dilemma. Either Warwick gets some good and relatable qualities or his lore gets set up in a way in which he still reigns as a villain who ends up winning mostly rather than get trashed by flaws for the sake of having flaws.
An example scenario is where Warwick actually has a conscience and he thought that the potion would cure him of that. His quest to obtain Soraka's heart (lol) would then be split between whether he can actually bring himself to do it and become a monster without need of the potion or he simply lets go of his grievances and lives with his guilt. This then lends itself into the question of whether or not Soraka would let go of her hatred and forgive him in order to help him. As of now there's literally no reason for her to help him and letting him go feral and eventually be put down is actually in her best interests.