I can't emphasize with Misaki at all. I understand you have your problems and all, but in no way will a bully gain my empathy by projecting her problems onto somebody else through bullying. I haven't read the LN and I don't know at this point what's Misaki's backstory, but with her nasty personality and behavior, would you be surprised that she would end up with very few friends to support her through her problems? Her chances to overcoming her situation just got reduced to a slither, thanks to her own doing, and whatever her own problems were, she had no right to destroy somebody else's high school life.
While I understand that it is the victim's forgiveness what's worth the most, I doubt Rei would condemn anyone unless it involved Claire. I think you are too hung up in what the character feels and does, forgetting that is just the way the author wills it to be. It is not the first time the author has imposed his own world views on us through the characters, that be through the incest issue, the maid rapist, or the overly tolerant MC girl.
Unfortunately or not, I have a hard time strictly confining fiction to fiction, as I usually put myself in the character's shoes to discover my own response to the situation. My response in this case, would be no contact with Misaki throughout the rest of my life. She died? It is inconsequential to me. As a matter of fact, I would be feeling Schadenfreude almost, to think that the person that bullied me to become a shut in had collected her outcome. You might say this is messed up, but I think it is normal that you do not want to see the people who made your life impossible live a happy go lucky life, and feels satisfied when karma comes around to bite them in the ass.
Edit: Just came up with a very petty argument, was Hitler's suicide a bad thing as well then?
And, if bitch Misaki died because she didn't want to burden everyone else, too late mate. Is all your bullying not enough burdening for your entire lifetime? Didn't know any better huh? I hate the tropes where any heinous crime can be forgiven by a sob story and a sorry, never sit well with me, never will.
I think that a lot of this discussion is stemming from different definitions of bullying, and what it means to be bullied across generations and cultures.
As an example:
I am GenX (fuck, I'm old); I was also bullied in school.
In my generation, that meant having a literal broken nose at least twice a month, and having had fingers and toes broken on a regular basis; having a black eye simply meant that of the other kids had "gotten a little rowdy."
This doesn't include the words that hurt worse than that from the teachers and students, alike; the level of casual physical violence, verbal aggression, and social- aggressive assaults would shock most people today... even those of us who lived through it looking back in retrospect.
Now, I'm not saying that to whine or complain about my life, I'm pointing this out to note that when one of my bullies died of brain cancer I kind of chuckled, smiled, and said "I love that for him," and then moved on with my life.
...
But
That doesn't sound much like the bullying that we're discussing here, meaning that my reaction described above is pretty far out of line.
Honestly, I feel terrible for the fate of Misaki-kun.
Their story is so painfully real to me; I can see every wrong turn they made, and I suspect that their suicide had a lot to do with having bullied Rei-chan.
Also, being GenX, I've also had a few friends in my life remove themselves from living for this exact reason, and the first one was actually in high school.
As you can imagine, it kinda makes this story hit home.
I get that bullies are nearly unforgivable, but I'm thinking this isn't that kinda situation.
(P.S. - to your humorous petty argument: Hitler's suicide was terrible, but only cos he waited so long to do it; should've been done in 1934!)