@Knighto and
@OsoJr
The whole bullying as kids also happened under the leadership of Kyou.
That's the most messed up one of the lot and I think the only one of the group who actually had killing impulses from the beginning.
The other ones were also clearly bad to some extend, but I don't know for sure how far they would have gone had they not been influenced by him.
Pretty sure they would have been "simple" delinquents, rather bad but not psychotic killers.
Like in chapter 5, when we see Kyou explaining how to "maximize" the feeling of killing an animal. Mixing the feeling of love into a killing impulse. That's pretty twisted and not something Senkouji would have thought of by himself.
That said, he was never really a good person to begin with. Pretty sure Kyou chose this band because of their bully personalities.