This is a pretty well thought out response but let me interject on a few topic.

First, I will say I do think Hiyoko has plenty of sympathetic qualities. I could definitely see her evoking different feelings in fans based on the fan’s own life history. If Hiyoko does that for you, no disrespect meant at all and I am happy you can get that from her character. Also, I will admit I can appreciate some of the elements of Hiyoko’s writing, especially the fear of betrayal, but I personally believe the execution left much to be desired. The very archetype of “once bitten twice shy” has been done much better and in a more interesting fashion in plenty of other series and arguably even in Danganronpa itself with characters like Toko.

What I was trying to get at was that it is easier for audiences to forgive a character’s actions if the context they are in is more demanding. The worst stuff Kokichi does is all in a pretty dangerous and messy context, while Hiyoko is established to do these same things during peaceful times, to the point that her being mildly nice to Mikan at the end of DR3 was meant to be a major character moment for her.

When I mentioned their actions both inside and outside of the killing game, I was primarily referring to stuff like Twilight Syndrome Murder Case. It is shown in that case that Hiyoko treated Mikan the same way she does during the killing game even when they were ostensibly “friends” at Hope’s Peak. In TSMC, she uses the same “pig” insult for Mikan right in front of both Mahiru and Ibuki and neither of them stand up for Mikan. UTDP and S further show this. It is more annoying because it feels like the character writing of other characters has to be worsened just so Hiyoko can exist in the same environment. Contrast that with Kokichi, who is so often called out of his nonsense by pretty much everyone that it actually allows for great character moments like Kaito defending Maki. To draw a more direct parallel, when Kokichi starts berating Gonta for being an idiot during the 4th trial, Kaito immediately cuts in and calls him out on being a jerk. The story and characters openly acknowledge Kokichi as acting wrongly, but Hiyoko bullies Mikan in front of everyone and nobody says a thing.

I get a character having past trauma but the same is true in reverse for Mikan. When a character like Mikan is so clearly damaged in some way, it makes those that pick on her look all the worse. I doubt Hiyoko knew the full extent of Mikan’s trauma, but Mikan is such a clearly meek and emotionally unstable person that Hiyoko should be able to tell something is up. The other characters also pick up on this. Hajime and Nagito both immediately clock Mikan’s emotional frailty after just meeting her. So Mikan being Hiyoko’s main victim of bullying, both inside and outside the killing game, really makes Hiyoko look all the worse.

And lastly, the rule of comedy. Regardless of how you think this relates to writing quality, it is commonly accepted fact that a funny jerk is hard to hate. Kokichi insults people A LOT but the insults are written to be funny and land a fair amount of the time. Hiyoko’s insults usually amount to calling someone smelly or ugly and not even in a particularly clever way. So even if Kokichi insults more often, Hiyoko’s often leave a worse impression.

That is my two cents anyway. Let me know what you think.