No love (or uh Hate) for John Ratcliffe or Syndrome? The following are the Disney villains who attempted or succeed at mass murder
Frollo has of course already been discussed with his attempted genocide of the Gypsies among other vile offenses.
Rourke - Almost killed everyone in Atlantis so that he could steal the Heart of Atlantis. I'm not sure what to think of Rourke...his goal was not actually the genocide of the Atlantean people, their deaths would just have been a side effect that did not bother his conscience in the least. So does that indifference make him more sinister or less sinister?
AUTO - Attempted to potentially kill everyone on the space station by crashing it in order to prevent the discovery of life recovering on Earth. AUTO is just a computer programming that was essentially following poorly imputed orders...so not sure you can apply the sinister tag here?
Syndrome - Killed at least 15 Supers. (Exact number is unknown as there are multiple cutaways while the list of dead supers is being displayed). It seems that like Rourke he was apathetic towards these Supers, their deaths were nothing more than a way to improve his robot to make it ready to take on Mr. Incredible. Heck technically all the dead Supers even willingly signed up to fight the battle robots although they were under the false impression that the machine was malfunctioning. With that said he then does later try to murder the entire Parr family to hurt Mr. Incredible, with Dash/Violet/Helen not really having signed up for it. Plus he was okay with possible casualties during his staged robot attack on the city, and tried kidnapping the baby Jack-Jack at the end for unknown means other than REVENGE.
The Horned King - His ultimate goal was not really revealed as far as I can remember? But basically it seemed like he wanted to use the Cauldron to create an undead zombie army (also note that said army was partially made up of his own followers which the Cauldron killed) to wreak mass havoc and kill a lot of people and I guess rule the world? Clearly this guy was one of the most disturbing/evil/sinister villains.
Then there is Governor Ratcliffe. Ratcliffe was a special kind of vile villain with his attempted genocide of Powhattan's tribe. I mean just listen to some of his lyrics from the song "Savages" and tell me this is not one of the most screwed up twisted Disney villains in the head.
"What can you expect
From filthy little heathens?
Their whole disgusting race is like a curse
Their skin's a hellish red
They're only good when dead
They're vermin, as I said
And worse
[...]
Barely even human"
If it's possible for it to be worse then there is also the fact that when he was leading the colonists to kill the Native Americans (with more than a few of the colonists also likely to die in the conflict) it was under the false pretense of saving/avenging John Smith, someone that Ratcliffe could have cared less about (in fact he threatened to have him killed, declaring the next person to see an Indian and not kill them would be branded a traitor and killed) when the reality was this genocide was a mix of his feelings towards the natives and his belief that they had gold he could seize.
Finally
Ratigan also deserves a mentioned as one of the most sinister, although it's based solely on a single often forgotten line from his song.
"Worse than the widows and orphans you drowned?"
In other words he apparently enjoys murdering women and children...and the fact that both words were plural and that he apparently succeeded in the acts puts him a step above other attempted Disney child killers like Medusa in the sinister department.
