What is the work?[]
The Thing on the Doorstep is a short horror story written by H.P. Lovecraft about a man named Daniel Upton who starts the story trying to explain how him killing his childhood friend Edward Derby did not make him a murderer since, according to him, that wasn't him but rather something piloting his body.
Who is he? What has he done?[]
Ephraim Waite is the main antagonist of The Thing on the Doorstep who was a half-mad practitioner of the dark arts and a frequent participant in rituals going by the nickname "Kamog." He would get together with a native from Innsmouth and has a daughter named Asenath who he dislikes because she was both born as a female and she was not fully human. He is one day assumed deceased but the truth is far worse: in trying to find a way to extend his life, Ephraim would take his own daughter's body as his own, trapping Asenath in his original body and poisoning and locking it away. However, Ephraim would desire a male host which is where Derby comes in.
Derby would marry Asenath, but he would realize something is wrong. In one instance, his conscience gets taken to another plane where he sees shoggoths and speculates that Ephraim was not actually dead. As he needed a male host with a weaker will, Ephraim would jump into his body now and again driving him more and more to madness. When Daniel goes to pick him up, Derby rambles saying that he suspects that Ephraim is piloting her body such as whenever she would write and her penmanship would resemble her father's. However, Ephraim takes over Derby again in a false reassurance that there was nothing wrong.
Eventually, things seem to return to normalcy but it turns out that Derby murdered Asenath and thought that would be the end of it. But unfortunately, Ephraim completely possesses him and flings his conscience into Asenath's body... which was decaying and buried underground. Through sheer luck, Derby is able to drag himself out and goes to Daniel being the eponymous thing on the doorstep delivering his best friend a message to go to the sanitarium and kill Ephraim, preferring that he also cremate the body to keep Ephraim from returning.
Freudian Excuse? Mitigating factors?[]
No. He is your typical mad cultist who is trying to live forever.
Heinous standard[]
It should be pretty evident but the Cthulhu Mythos has a huge heinous standard with the likes of Nyarlathotep (who may end up getting reevaluated since him being monstrously evil was added by other contributors to the Mythos later). As for the human characters, we have a few heinous ones. There's Old Whateley who hands his daughter over to be raped by Yog-Sothoth and later tries to indoctrinate his grandson into opening the gates to allow the old ones to return which would mean the end of the world. Then there is Keziah Mason or Nahab an old, decrepit witch who sacrifices hundreds of infants to Nyarlathotep in return for her learning interdimensional travel. There is the villain from "The Temple" who makes the habit of destroying lifeboats on the regular. And there is Obed Marsh from The Shadow Over Innsmouth who starts a system where the residents had to mate with Deep Ones and provides human sacrifices.
Ephraim has a lower body count, but I think he edges by (in terms of the OG Lovecraft writings as the others coming from other authors are dubious) with just how nasty his plan is. He subjects his own daughter to be trapped in his old, rotting body when he uses hers and even poisons it to make her suffer more before moving onto Derby. He drives Derby to insanity whenever he possesses his body to the point Derby kills his wife to free himself of him only for that to fail and he would be possessed by Ephraim anyway. This leads to Derby begging Daniel to go to the sanitarium and kill the "imposter" saying that all Ephraim wanted was to hop from body to body forever which could spell havoc on the world. Worse as Derby himself states, when he gets trapped in Asenath's decomposing body, he is fully aware and suffering.