OMG! I just remembered this one, and I’m overexcited. What an insult. I don’t like that is so superficial: it means “to be ugly as hell / to be incredibly ugly”, but anyway.
el aborto: miscarriage
el diablo: Satan
I haven’t heard it in a long time, I don’t know if it’s falling into disuse, or it’s only for cultured insulting. A quick Google search threw me into post comments of angry people.
For example: “No vales nada, eres un aborto del diablo”. So much hate. Very angry. ‘You’re not worth anything, you’re Satan’s abortion’.
Let’s take a moment to remember that this is a linguistic research. Hate is ugly to receive, but the one that loses the most is the one that does the hate. You could be in YouTube, wasting your life pleasantly, watching dog videos, but no, you are in the comment section of whatever site fighting someone you know nothing about.