I think that is quite clear. I think he meant he was trying to make the most evilest seme. Like dom in a gay relationship not in bdsm.
Idk, you could be right, but 'dom' is such a specific term to use.
Err that could be the translator mistake, you know Korean seme and uke is gong and su right? ( read chapter 4 if you need reference, dong Hyuk print the whole shit from the internet) but maybe because the translator doesn't want to translate it as seme (it's the official translation so maybe they don't want do it with Japanese influence). That's why they translate it as dom instead of seme.
"I wanted to make Yule the evilest dom ever."
Wait. Dom? Dom as in BDSM dom?
You HAVE to be kidding me. I would never consider this story to have anything to do with BDSM. BDSM involves trust and understanding your partner, not causing lasting harm, threatening death or causing psychological abuse. That's just downright terrible. Talk about not doing your research.