I have complicated feelings about Kokichi! In many ways, I really enjoy him; he'd probably be towards the top if I ranked the V3 characters in order of how much I like them. I think he's a fascinating character, and a fun one, and I don't think he's as malicious as he makes himself out to be. But I do think people sometimes downplay how cruel Kokichi can be.
In particular, what Kokichi did to Gonta was absolutely horrendous. If Kokichi saw Miu's murder attempt coming from before he'd even gone into the virtual world, there were probably ways to avert it that weren't 'manipulate someone else into murdering her and getting executed for it'. And he evidently wasn't sincere in his 'let's put everyone else out of their misery' suggestion, given that he flat-out named Gonta as the culprit at the trial.
Kokichi screaming at Gonta in the fourth trial really gets to me. You've done enough to this poor boy already, Kokichi! You drove him into despair and forced him to commit murder for you, and he's going to end up getting executed because of it; you don't have to yell at him on top of that!
His constant insults to Miu sort of get to me sometimes, too. Which is a little silly, because Miu is constantly insulting everyone! Maybe Kokichi's insults feel harsher because they're specifically targeting a small handful of people, whereas Miu will just insult everyone and everything in range. Or, you know, maybe Kokichi's insults feel harsher in the knowledge that he'll eventually be responsible for Miu's death.
Which isn't to say anything's wrong with loving Kokichi, of course! I love a lot of characters who've done awful things; I made an entire Death Note website just so I could ramble breathlessly about Light Yagami. Komaeda's one of my absolute favourite Danganronpa characters, and he's also guilty of manipulating people into committing murder, for much less sympathetic reasons than self-defence.
Also, Kokichi is hilarious. I'll always love the fact that he took the important measure of writing all those witty and brilliant posthumous lines for himself while slowly dying.
I love that Kokichi's voice actor is clearly always having a whale of a time. Just being as obnoxious as possible and having an absolute blast.