thanks for answering my comment, please read all of this reply so that you won't misinterpret my pointIf a person being bullied finally stand up one day, then the night after he cowers in fear upon what may be brought to him the following days of his remaining school life, and he shows some sort of regret, does it mean the person should not have stood up against bullying? Just because a character shows a sign of regret of doing something does not mean he is in the wrong (or that he shouldn't have done it).
Your whole argument for the rest of the paragraph revolves around blaming MC for doing something because he regrets it. There are many things in life a person may regret doing, but does not necessarily become 'wrong'. There's a reason why that teacher has been able to keep doing what he has been doing (presumed by the reaction when he got found out with zero remorse). Either the local judge is fucked up, or he's so cunning he plans everything straight that he is certain he will get away with it.
For your first point, yes the situation of bullying that you said is completely right, but THAT'S BULLYING, not raping and murder!!! They aren't even comparable since they are severely different
Secondly, you said that "even if he regretted doing it then it doesn't means that it's wrong", bro
are you trying to say that killing someone is somehow not wrong? (probably not, I would hope so), of fuckin course murder is always wrong (logically speaking), the reason everyone can get behind why he killed the asshole is that that piece of trash deserved it (it's emotional right instead of logical right) and this I can 100% understand and agree, you can't demand anyone to do things logically in a situation like that. Besides, in this case, it'd be fuckin moronic if the main protag didn't act emotionally. If he didn't act emotionally and didn't kill, it would mean that he didn't love his lil sister enough to go rampage when he found out about the situation.
And it's not clear whether the teacher has done those deplorable acts many times before or not, maybe he said the thing he said because he's a straight-up shitbag and he wasn't even slightly remorseful of what he did even after he was caught, and since it's not confirmed whether he has raped other girls or not, both you and I can't really use it as a fair point (you could be right on this or I could be right) so to make it a fair argument, let's cast it aside since it hasn't been confirmed yet
And in my comment, I said that he shouldn't have killed, not because he was necessarily wrong ("wrong" here means without any right reasons, like I said murder is not right but it doesn't mean that you can't have a right reason to do it) but because his life would've worked out better if he didn't kill, (which I know is moronic considering that we don't know if he hadn't killed, the bastard would be caught and put in jail or not ), but there's one thing for certain, which is if he hadn't killed, he would not have gone to prison and his mom wouldn't have seen her only child left to leave her for 7 years, and the pain may cut deep but after a long enough period of time, the both of them could move on from their grief, which would be better for his mental health anyway. And from his perspective, him living and getting over the grief is much better than wanting to kill himself every second of the day after (which was caused by his murder), and you gotta admit that that would be a better outcome even just for his own sake
So to cap off, my point is that the main protag was not entirely wrong when he killed that bastard, it's just that things could have worked out better for him and his mom's sake (and maybe the girl too) had he not killed. That's it