Without spoilers, Byakuya and Kokichi are objectively bad people.

With 1, UDG and v3 spoilers, Byakuya is way too rude to everyone for no reason and it isn't likeable. It was a bit more endearing towards the end of THH when he starts to warm up a bit, but then he never really changes. The worst is when he is saved by Toko after being captive for days and still immediately insults her. Also messing with Chihiro's body and the crime scene was a psychopathic thing to do for his own benefit and he clearly didn't feel bad about it.

Kokichi has a good goal in mind but the ends don't justify the means. Getting Miu killed, selling out Gonta and keeping up his whole evil persona was completely unjustified. His explanation that he needed everyone to seem him as the villain for his plan to work just isn't true either. He could have cooperated at any point to create an unsolvable murder with everyone. And with everyone on board, it would be more likely to succeed. He is cruel to everyone basically any time they are mourning, and there's no good reason for it.