Stuff of nightmares (for a young reader at least) : Ben Reilly (briefly bonded with Cletus Kasady's symbiote) turning into Spider-Carnage. Evil Ben done right (not that current Chasm crap). Terrific mid-90's art by John Romita Jr. & Al Williamson from 1996's Spider-Man #67.
It's practically the same formula of "break up make up" as Eddie and Venom in Let There Be Carnage. What did he do, Red? Did you just get bored waiting around Ravencroft?
(...Homophobic, alien-phobic Spider-man always trying to break up happy relationships 💔)
We have never strongly considered Spider-Carnage for the Wishlist. It's hard to research how often this persona has surfaced, but it has been in comics and TV. It's basically a Spider-Man (Peter or a clone) paired up with Carnage.
Should [the editors of the MCOC Wishlist] care? If the criteria is “belongs in the top 600-ish characters to consider for MCoC, is this mashup probably too obscure?