* Alien Bado, with his Elephant Man head.
** The (allegedly cute, bird-like) Guts aliens with their deep voices, ghostly appearance (at least inside their space vessels) in "Seven Assassination Scheme", and for that part, their plan (capture and execute Seven) and tactics [[spoiler: (appear and disappear out of nowhere, accost Dan to make him transform and fight, wear Ultra Seven down, crucify him, execute him in front of the whole world)]] are disturbing to this day.
* Then there's that gas-guzzling... thing from "Space Prisoner 303"... the feral Alien Icarus from "The Strange Neighbor"... the faceless dudes from "The Fugitive Fortune Teller"... Perolinga, the inside-out chicken alien thing in "Flying Saucers Have Arrived"... [[BigfootSasquatchAndYeti Alien Wild]] in "Fly to the Mountain of Evil"... Alien Spehl from [[BannedInChina Episode 12]] (a mummy-like creature with glowing welts, a deep voice, and an even deeper growl), especially as it emerged from his hideout, scaring children who had been lured there with the promise of a prize...
* For women tropers: If you knew what was hiding inside an unsuspecting girl's body, you'll never smell a flower up close again. Amagi's fiancée found out the hard way in Ep. 31 "The Flower Where the Devil Dwells".
* On that same note, women were dying to own the latest Japanese watch, literally... [[spoiler: [[OurVampiresAreDifferent Aliens were feeding off their blood]], that is, until their attention turned to children.]] By the way, this happened in [[BannedInChina Episode 12]], featuring Alien Spehl.
* From "The Green Terror": Imagine you turn into a plant against your will, then go on killing rampages across the neighborhood. Now picture your spouse and you going on a vacation trip by train and that happens to you, right in front of all the passengers.
* The Ghos aliens' plan to force earthlings to live underground as slaves in Mars (or here on Earth) after destroying the surface, beginning with Paris, London, [[HarsherInHindsight New York]], and Tokyo.
* Alien Chibull from "Android 0 Directive" builds and gives away war-related toys that happen to be real weapons, so that all children can wage war and force adults, who (supposedly) won't fight them, to surrender. [[FridgeHorror What's to stop a determined or desperate grown-up from fighting back, regardless?]]
* King Joe can be kind of freaky sometimes. Also, while Metron is [[FriendlyEnemy pretty cool]], the fact that he works by ''causing violent hallucinations'' and is responsible for hundreds of violent incidents in the town he's in is quite scary.
* [[OffWithHisHead Eleking's death]] is pretty graphic, to say the least.