I understand Severus to a nearly unreasonable degree.
"But he joined the death eaters!" Okay? And? His father was a muggle who was terrible to him and others, if there was a military hate club, I'd join too! I hate the military for no reason, purely because of my dad, so, given that he actually had a reason, it's understandable.
"But he's mean to students!" Bro, I would've been fired years ago for child mistreatment, I'd be throwing desks, shouting, etc— hell no.
"But he just walked over James' dead body!" Cool, and I would've taken a selfie, like?? Iconic king?