Complete Monster Near Miss: Flamebear from GalaxyClan
Note: GalaxyClan is on Hiatus and Flamebear is not double dead yet. This could end up being outdated, either through Flamebear somehow partially redeeming himself or actively shedding his few redeeming qualities.
Heinousness Standard: Passed.
Begins poisoning Hollowstar even before his corruption into a serial killer, deeming him unfit to rule the Clan.
After killing Cavernbounce, he notices he had a witness in Micakit and forced her to kill Pond. He also forced Gustkit to kill Echolily. Both Micakit and Gustkit were children.
He begins poisoning the freshkill pile and mistreating his patients, leading to several deaths in the clan.
In year 19, he murders his own son Dreamsmoke by force-feeding him deathberries and manipulates Hollowstar into killing Springhaze by pinning all of his horrific actions on him.
Attempted to corrupt Todd in year 20.
In year 22, he manipulated Scratchfleck into placing tainted prey into the Clan's fresh-kill pile, leading to the death of him and three other cats, his old apprentice Snakeeye included.
Lack of Redeeming Qualities: Not quite (see below)
Other Qualifying Factors: Pass.
It's worth noting that Flamebear was actively influenced by Butterflypaw, but this doesn't affect his moral agency because 1) she simply tapped into what was already there, and 2) she didn't really think that Flamebear would go this far.
To some extent, he sincerely believes that his actions will benefit his Clan in the long run. His thought process is that if cats die now, then more cats won't die later or something. The narrative treats this as redeeming.
Despite killing their son, he never subverts his care for Sleekclove. In fact, it's in part due to his grief for him that gave Butterflypaw and Frecklespot the opening to corrupt him.