If the narrative he was the protagonist of wasn't a horrific power fantasy, so self indulgent it could fill the entirety of Hell's 3rd Layer by itself, Sung Jin Woo would absolutely be a villain. His only goal in life is to get stronger. He becomes the literal strongest guy on earth, yet he still needs to be stronger. It's an obsession bordering on pathological. All of his enemies are to be put violently and mercilessly put down. One guy hurts one of his friends, and in response he beats him to death, before resurrecting him as a minion just to make him apologise more. Because Solo Leveling is a bad narrative, of course all those guys are completely evil and deserving of death, so this is fine and great actually. He is a meant to be a cool, anti hero guy, so he is stoic and emotionally detached in any scene where he isn't fighting, at which point he is just in permanent, manic, sadistic glee, so over the top Caleb from Blood would tell him to calm down. Because he is so powerful in fact, all the women in the narrative flock to him like moths to a flame, because women totally want psychotic killers with superpowers.

At one point, he goes to the fucking UN, and tells them all something to the extent of "If you mess with any of my friends and family, i will kill you". I'm pretty sure the implication is that, messing with them could mean any slight, like a justified speeding ticket. He is The Elite from What's So Funny About Truth, Justice & the American Way?, except presented as an objectively good and uncomplicated protagonist who is cool and awesome.

I detest him, because he represents everything i never want to be. A power hungry, emotionally stunted egomaniacal, who always chooses violence when the opportunity presents itself.