Regardless, it still doesn't make Sid right. His arrogance and selfishness will kill him.
The reason why I have no sympathy for Sid is the way he treated Jinyoung as his possession like his love/worship for Cain, and the way he betrayed Cain's trust and kindness. Let's not forget the many times he tries to undermine Kyungjoon and get him killed.
There's a lot of unforgivable things he's done that I just can't seem to find myself sympathising at all, as hard as I try to give the benefit of the doubt.
I think Sid is supposed to be that character everyone hates on. Doesn't matter what back story the author gives him, it's brushed under the rug by the many times he keeps trying to force himself onto Jinyoung and continuously hurting Cain, along with finding ways to kill Kyungjoon.
I think by the time I finish reading this manhwa, my views on Sid will remain unchanged.
your mind is asking for my love and you just need to hear it...
(I'm very opinionated and will rant so if you've seen my comments, I'm sure you'll see me more)