Transformers: Beast Wars is a very violent show, exploiting the Mecha Mooks loophole as far as it can. Characters are bashed up, blown apart, shot, stabbed... This is not a show for children under ten, having been written with an eye towards not boring those who grew up on the original Transformers and were at that point in their teens and twenties.
Tarantulas, is essentially, The Mad Hatter without the whimsy, and very much a sadist, which is hinted at with the exchange below. Toss in good ol' arachnophobia and you have yourself one of the most horrifying Transformers characters ever created.
Cheetor: This is a dumb plan, web-face. I don't have any real blood, just mech fluid.
Tarantulas: Oh, my filters will adjust. It's the act I enjoy more than the nourishment.
Despite the tragedy of the character, Rampage, definitely qualifies for this trope:
His backstory establishes him as a failed experiment created by the Maximals (y'know, the good guys). The original mission of the Axalon was to dump him someplace far and barren.
On Earth, Rampage is reactivated in "Bad Spark" and proceeds to tear Tarantulas limb from limb (offscreen). Blackarachnia and Silverbolt come across Tarantulas's arm hanging from a tree and laugh about him being "disarmed". They later discover the rest of him, and are subsequently attacked by Rampage.
It takes the combined efforts of Silverbolt, Blackarachnia and Optimus Primal to shoot him off a cliff, making Rampage The Juggernaut in a Slasher Movie.
To top it all off, he was invincible and insane, and murdered and ate an entire colony of Transformers. Making matters worse: It wasn't actually a Transformer colony, it was just defended by Maximals, Meaning.....
Despite all the above, what Megatron does to his spark in this debut episode is arguably even more terrifying:
Megatron finds Rampage damaged...and proceeds to cut his spark in half offscreen. Back at the Predacon base, once Rampage is healed, Megatron holds up Rampage’s spark in a box-like contraption, the spark held between several spikes of Energon, which he then squeezes, causing Rampage to yell in pain. Then Megatron proceeds to force Rampage to join the Predacon ranks, all while doing a creepy Evil Laugh.
Later in the series uses that part of Rampage's spark to create an evil Transmetal 2 clone of Dinobot, who has no compunctions about torturing the spark to compel Rampage to continue to obey him, while he seems unhurt by it, and does so almost every time with a dementedly sadistic grin on his face.
It's more disturbing than that. Both of them show the same crackling pattern when the spark is harmed. Dinobot 2 is feeling exactly the same pain, and doesn't care at all
Transmutate, the malformed, mentally stunted, childlike being from the episode of the same name was deeply unnerving. The fact that she was then blown up by the two Transformers who were trying to protect her didn't help...
A part of the disturbing nature of this character is how brazenly it captures a mentally-stunted character. It's overall a surreal episode, given its place in the series: an action-packed, tragic game-changer episode just preceded it, and the next three episodes would go on to truly solidify the series' place in the Transformers canon with some epic revelations, and sandwiched in the middle, we have this odd, docile episode about a mentally stunted robot that is just "not quite right".
Proving once again that this is a subjective trope. Many fans actually saw her as The Woobie.
Cheetor's dream in Feral Scream is pretty disturbing, particularly what Cheetor transforms into in said dream.
Cheetor's roar echoing across the landscape in the dead of night.
Feral cheetor's first appearance sees him stalk and dispatch a whole group of predacons, including Dinobot2 and Megatron, all the while moving too fast to be seen clearly. The scenes in between the attacks are very tense and paranoid, particularly when Megatron panics and shoots Waspinator by accident.
There was a scene where Megatron goes to the Ark to steal his ancestor's (That would be G1!Megatron's) spark. Instead of cutting it out like he did with Rampage, he does something even more horrifying. He uses a tentacle like appendage to rip his ancestor's spark out.
Then there is what Megatron does to Dinobot after his sacrifice. He took their greatest hero, and made a clone of him more powerful and dreadful than ever. Megatron made him into a horrible insult against his memory on purpose and every scene featuring him felt like a horror movie to this troper. Now, try to imagine how it must have felt for the Maximals, especially Rattrap...
Worse, there were talks of an unproduced episode idea titled "Dark Glass", where Rattrap would try to probe Dinobot II and see if there was any trace of the original's personality beneath the fierce clone.
Given that sparks = souls, it is instructive to contemplate just how much Predacon technology revolves around horribly abusing them. And that at least some of the characters don't just end up dead, but with their sparks utterly extinguished. Forever. This doesn't necessarily mean "oblivion", just that their sparks are blasted out of the physical universe forever and forced either into the Allspark or the Pit (Transformers Heaven and Hell, respectively). To say nothing of all the Mind Control.
Megatron's last resort was to wipe the entire Cybertronian race from existance by killing Optimus Prime (and thus the Matrix) before the Great War could end. This would pretty much wipe everyone on the show but Tarantulas (and that's only because he's got Divine Parentage in the form of Unicron) from existance. It's thusly no small wonder that Megatron is reluctant to go through with it.