The two pilot episodes of the series are truly disturbing and unrealistic, considering some Nightmare Face that the duo does, and some deaths in the same episodes. Still, they are considered as Negative Continuity.
First and foremost, the episode "Bungholio: Lord of the Harvest" features a the old janitor / farmer who speaks quietly and attacks Butt-Head while advancing upon him offscreen. At the end, the zombie farmer and a now blue-skinned Butt-Head advance on Beavis with chainsaws and violently murder him offscreen with only a single drop of blood hitting the screen. All as Beavis screams until he falls silent and the barn door closes by itself.
There's also that deranged look Beavis as Cornholio gives the camera (from a child's POV) as he claims all of Tom Anderson's trick or treater candy for himself.
The farmer appears in the earlier episode "Cow Tipping" where the two try to tip a cow. Beavis becomes trapped under the cow as the zombie farmer appears with a chainsaw readied to kill him. It then cuts to black, with Butt-Head standing there, laughing as Beavis is presumably hacked to nothing.
Beavis and Butt-Head's screaming faces are pretty unnerving in an off themselves, putting the "Deranged" in Deranged Animation.
Want a good example of how creepy he is? Watch "No Laughing" at the part when he tries to get Beavis and Butt-Head to laugh by saying sexual words. The closeups to his bloodshot eyes and deranged face are unpleasant.
Another example occurs at the end of "P.T.A." when Beavis and Butt-Head mention in passing about Buzzcut kicking their asses. In the very last seconds of the episode, Buzzcut receives a letter from the administration. His reaction is as such:
"Your abuse of two students has come to our attention"? Who are they?! I'LL KILL 'EM!
Amusing Injuries aside, seeing Beavis with his burnt ass in "Butt Flambe" is both disturbing and painful to watch. Just seeing and hearing his cries of agony is enough.
"Nose Bleed" is not for the squeamish, as it features Beavis bleeding horribly after being punched in the nose too many times. To make matters worse, Butt-Head's attempts to "help" Beavis just result in bigger blood loss.
There is an episode where Beavis and Butt-Head shoot down a plane while trying to hunt ducks. Then we see the people inside the plane crying for help, and, aside from weakly attempting to open the door, Beavis and Butt-Head leave them to die.
In another early episode, Van Driessen gets attacked by a bear that is pretty disturbing in appearance.
Van Driessen in general is subject to grisly fates throughout the series. Another very notable example is in the bus trip episode when the bus braking causes Van Driessen to fly through the windshield and fall down the side of a mountain.
Todd is creepy in himself. He's a ruthless thug who repeatedly beats up Beavis and Butt-Head and gets away with it due to being a brute and the duo's admiration of the jerk. And really, he has no redeeming qualities whatsoever.
"Wood Shop" is a revisit to the "Beavis bleeding horribly" element. The two are in wood shop class and put everything to be cut in half by a table saw-including a phone and a first aid kit. Then Beavis cuts his own finger off, leading to a massive amount of bleeding.
Beavis' dog bite wound with its exposed bone and the end where the doctor that administered the rabies shots is laughing ominously in a dim-lit room
"Breakdown" is truly a disturbing episode where Beavis and Butt-Head's inane laughter over the intercom finally drives McVicker to suffer a terrible mental breakdown and things only worsen when they visit him at the mental hospital. Then the episode ends with ominous music as their indifferent laughter begins to drive Van Driessen insane...
Really, Beavis and Butt-Head's indifference to the suffering of others really makes them turn from comedic Anti-Heroes into full-blown Villain Protagonists.
There's also the Big Lipped Alligator Moment from the film. As awesome as the music of White Zombie is, the visuals are sure to creep people out, such as the image of Butt-Head melting into a gang of miniature demonic Butt-Heads or the two headbanging as their skin flies off.
In "Werewolves of Highland", Beavis and Butt-Head set out to become undead so they can score with women (after watching Twilight and seeing how the girls fawn over Edward and Jacob). How do these two "brain surgeons" do it? They become sickly sore-covered STD victims after being bitten by an infected bum they believed to be a werewolf. What's more, said bum has been arrested for biting others in the past.
And while we're talking Nausea Fuel, there's "Tainted Meat." Beavis' wiener is itching terribly, and he can't stop scratching it even at Burger World. We get this really unnerving sequence of Beavis taking his hand out of his pants long enough to put some more burger patties on the grill, without washing his hands. The result is a montage of everyone in the restaurant keeling over from food poisoning. Butt-head, surprise surprise, barely notices, and wishes a horrified customer a great day.