After Luciel took a bath, he went to their space to play some games. No one would enter their room anyway except for Treyton, so it's okay to go to their space to have more time to play.
A while ago, he actually wanted to kill those scums already. The best way to prevent people like those from committing their crimes again was to directly kill them off.
Unfortunately, he was still sober, so he didn't end up killing them. He knew that it would just be troublesome if he really killed them off directly.
Anyway, it is also better for them to feel some pain and suffer while they're alive for all the things that they have done. Even if it's only a fraction of what they had done to others, it's also good to let them experience some of it.
Treyton and the others would surely do something, so even if Mr. Adel and his group survived, they wouldn't surely live more miserably than others.