Killer Combatant Series #1! Wraith barely takes the win! Voting over!

You can't send someone insane if they already have no sanity left.

This would render doc useless.

Maybe make it about only human ones. Like legion, and huntress. Because technically pyramid head would win, since he is immortal. And we know nemesis would win out of all the mortal ones. Not saying you should, just throwing out ideas :)

I'm not buying the whole "well wraith kills people so he's obviously insane" shtick because then that could just be applied to every killer across the board. That's just not how insanity works- it's a broader term but "usually reserved for describing severe conditions involving psychotic-like breaks with reality."

You can be a murderer and still be completely in your right mind and know exactly what it is that you're doing. People that are mentally unhinged may be more prone to violence, but there's a very large gap between unhinged and certifiably insane. Truly, I don't think we have a single "Insane Killer" on the entire roster and we've yet to see one. Perhaps you could say the Doctor himself is insane but if he was performing valuable research for the CIA it's difficult to say whether or not his sense of reality was intact, if it wasn't then I doubt he'd be learning anything valuable. However there is the line in his lore: "Carter's experimental information extraction had turned to horrific and bizarre torture" but again it's difficult to say whether this is could be Carter working to uncover secrets of the human mind by pushing well past scientific ethical boundaries or if he's well and truly insane and he only "thinks" he's still doing valuable research and in reality he's making false connections in a broken reality- not real science anymore but simply human cruelty.

Aside from that the closest things we have to insane I would say are Ghostface and the Trickster- not because they've got broken perceptions of reality but because they are very obvious psychopaths. Charming and likable on the outside and pretend to care about others, but are completely cold-hearted and fail to form genuine attachments, opting to have completely shallow and fake relationships in order to maintain the facade of a normal life to cover their criminal activities.

But they definitely understand what they're doing- both killers have a twisted sense of pleasure and gratification from their violent acts and a sense of accomplishment or achievement for their respective "performances". (Ghostface performs for newspapers, the cops and local authorities, and enjoys the attention of the horrified public eye. Whereas Trickster performs for an oblivious loving audience / adoring fans and the undivided attention of his victims who are subject to his torture- the contributors to his "art").

EDIT: The Clown also- at least for a brief period also falls under a similar form of psychopathy. Using the circus to escape his crimes and surrounded by a close-knit community he was forced to learn to socialize: "He donned a new personality like a disguise, quickly becoming known as charming and helpful, and was welcomed into his new family." However this doesn't last and he falls back into bad habits and violent tendencies and the Clown unlike Trickster and Ghostface drops the charade: "He removed the costume less and less, shedding his old personality with it, fully embracing the clown, his true self." Perhaps making him closer to the behavior of a sociopath- who unlike Psychopaths who are more manipulative, detached, and meticulous in their planning: "Sociopaths experience anxiety and find rage far harder to control. They may act without thought and, as a result, they may have a harder time blending in. Inconsistencies between their words and their lives may be easier to see." which aligns perfectly with how the Clown eventually became complacent and sloppy.

Every other killer has some kind of motivation for why they kill: Ambition (Blight), Rage (Oni), Vengeance (Deathslinger), Fear (Leatherface), "Justice" (Pyramid Head - manifestation of guilt), Devotion (Plague), etc. so on and so forth so I'm just not sure that this necessarily means that they wouldn't be susceptible to The Doctor's madness.

NOTE: Yes I am entirely aware that I totally went off on a tangent- however, seeing as I wasted literally an entire hour on this train of thought with a bunch of research and lore digging and everything I'm still posting this comment. Even if it is completely unrelated, meant absolutely nothing, or is completely wrong, at this point too much time has been invested to just delete it.

TL;DR Killers are not completely insane, though likely many if not all are somewhere on the spectrum of mentally unhinged. Ergo Doctor's madness still works.

The Doctor's madness aside, he's still imo one of the more powerful killers in the entity's realm electricity is a high key busted supernatural power to have. And outside of the game from a lore standpoint- in a brawl with other killers he could up the voltage for more painful and devastating damage. At the current level of intensity it's enough to paralyze the survivors motor functions for a brief moment- long enough that they can't even raise their arms to drop a pallet or move their legs to vault a window. A similar effect could be easily reproduced and used against the killers (even if a greater voltage was necessary) and I could totally see the Doctor shocking one of the other killers right before they were to land an attacking blow. Also we see the Doctor applying a high enough voltage to kill a survivor directly to their brains during his mori- so there's also that.

And physically I don't think there's a lot of question regarding The Doctor's capabilities, dude literally tore the sleeves off his lab coat to show off those guns attached to his torso. I'm not saying he's the strongest killer out there- but it definitely doesn't seem like he's lacking either and I would say he's on the physically stronger end.

I dunno, Wraith's pretty strong. He ripped an entire man's spine out, but who knows what Doc has underneath that smile of his...

Well... other than that, definitely other than that.