Alright, I managed to read through it all, it was faster than I thought. Yay! If I make any mistakes, sorry. I had some trouble telling a few characters apart and wasn't always clear who was doing what (I have the same issue with manga and anime, I'm not good with this xD).
Reading through all of it actually kind of makes me find his actions even more inexcusable . I could assume from the first few episodes I read that he probably has a traumatic backstory and that there's a reason he's doing this, but that doesn't change much. He's known joy, kindness, and love, which is from his mother. He's also known it for years from Olivia (even if eventually she turned on him), also for years, so he's not particularly cruel in an ignorant way. He knows what he's doing. It stands to reason that more people than just his mother are capable of kindness, but he still murders people at school, traumatizing other innocent students around him, and murders the man beating up the senior (thus traumatizing the senior after the senior was traumatized by his attacker . He just saw a murder happen. That sticks with a lot of people for years ).
While the man certainly deserved some kind of punishment, even the victim didn't want his life to be ended, and the crime was against him, not Dan. Dan doesn't hesitate, and not only does he not hesitate, he rejoices in killing him?
I can see that in Dan's mind, he, of course, is not the enemy. His perception of the world is that everyone is cruel (also...he's judging all of them before he's met them ), so he's responding to what he believes is a society completely and entirely against him. I'm not even sure if I can say his intentions are well-meaning, because I don't know if he literally means he wants to kill the whole world (which is the kind of ridiculous motive a villain will have), or if that's just his grand way of speaking. And I don't really care at this point because he's irredeemable to me.
I think maybe there's a different story going on in your head and that when it's written and drawn out, the execution tells a different story. I'm not sure. I've definitely done that a few times before and am always wildly taken aback by the conclusions some readers come to. There's never going to be 100% accuracy when it comes to the stories in our head vs on paper, since people make their own interpretations.
The biggest thing I'd say that would have to change to sway me, would be the pure joy he seems to get from doing what he does. That's exactly what a psychopathic killer does. No way around it. There are some people in the world I find truly disgusting, and while I'd never feel guilty if given the choice to be rid of them I'd never feel joy in playing with their lives, either, or go around laughing and strutting about like I'm the coolest thing since sliced bread. And I think that's the line for antiheroes vs villains when it comes to murder (in addition to the murders having to be more reasonable. I can get behind).
This is not to say it's wrong for victims to be happy when their perpetrators are gone, or to wish pain on their perpetrators. That makes sense. I think there's a line between actually going through with the torture, enjoying it, and showing absolutely no second-thought on the murder at all and then continuing to go and kill others who've not also made extreme, grievous offenses, VS being glad the person who hurt you is in jail, dead from painful battle with cancer, or something similar. Especially when the murdering is with your bare hands. That's extremely personal, like choking someone out, as opposed to using a bullet from a distance. Someone who kills with the latter are often people who'd never do the former.
Dan's a villain. That doesn't mean he can't transition from villain to antihero. But he's definitely a villain, and preferably needs to make that transition soon as possible. The longer he goes on as a villain, the harder making a believable transition to antihero will be.
Please don't take that as me telling you what "needs" to happen in your story. I get the sense that you want him to be seen as an antihero, so I make those suggestions, out of knowing what would help me see him as one, but I'm not a reader of this genre and don't understand the intricacies of what is supposed to be passed off as a staple of the genre and not. ^^
It was also really cool to see your art improve as time went on! Lots of great looking panels and the guy with the dreadlocks seems interesting. Good luck with your story!