I'm a well read grad student who's bluntly honest about all things, although I try to be most honest about myself.

Spoiler-y stuff behind the page break. Serious, major spoilers. And possibly more crying.
I know that worse things happen to Viv. I also know that they'll both recover from this. Given what happens to Vin later on, this is especially distressing:

I have to say, I love both Viv and Vin. Maybe it's the death factor that makes me think I like Vin more, but, yeah. He seemed to be more sensitive and introspective. Viv is smart, but acts more with her heart, and I love Vin fiercely for his quiet thoughtfulness. To watch his sister get gutted, then get attacked himself, must have been quite a traumatic event for him, and then it's compounded by watching his mother murder the attacker and being told to stay quiet about it all.
This is heartbreaking because he had a short life, full of confusion and even, yes, trauma. And of the two children, I was most looking forward to seeing the adult that Vin would become. I didn't want any of the Visions to die, but suspected they would kill off Virgina if they killed off anyone. And then that they would when they said one would die. The relationship she has with Vision constantly teaching her things is weird and a little gross: he's obviously got more power in the form of more experience at, y'know, living, particularly living amongst humans. The children were growing so it was a little less awkward. Also less awkward because they weren't, say, seducing Vision ever.
Killing off a child is a drastic step to take, particularly with the other issues going on in this comic, and particularly with how they did so: an accidental death by a family member who couldn't really control his own powers. Although I wonder, looking back at this panel, if they knew Vin would die and were somehow hinting at this here. Even if not, it's a heartbreaking panel.