It is pretty much a neverending cycle of being betrayed and lonely.
When his hometown was razed, his father was killed in front of his eyes and his sister was sold as slave to a noble. He is stuck with a never ending circle of grief and despair plus the building distrust on humanity. His time at Crowley did not save him either. Him getting physical is his defense mechanism to not being hurt at all again. And sadly nobody tried 'save' him this early.
Later on, Rein's mercy at Lobelia are also not seen as a compassion, but more as a mockery of Lobelia's life "....like an insult from those who are priviledged to those that does not live with the luxury"
Also this would continue to loop over as Lobelia kept being lonely and betrayed by literally everyone (even his sister later on). And he died, truly alone in every sense and betrayed by everyone. With nobody understand him.
You just convinced me more that he's retarded.
Hitting a classmate that ask you nicely just beyond dumb. Tragic my ass.
He deserves everything that coming at him if he's being that dumb. His new parents seems like a good guys (at least from this chapter shown, unless he secretly tortured him then it's a whole different story), but he's just lashing out at anyone and justify it as "DefEnSe mEcHaniSm" bs.