"People can list any number of reasons to be afraid. This is because at the most fundamental level, 'comfort' leads to 'life', whilst 'fear' leads to 'death'. While people cannot give a clear answer why they want to live, they can give any number of answers why they do not wish to die. Thus, it is impossible to be unaffected by fear as long as you are alive."
King Sombra's Magic Door (My Little Pony: Friendship Is Magic)
Left Hand of Horror (Grim adventures of Billy and Mandy)
Mansion of Night (Percy Jackson)
Freddy Krueger (A Nightmare on Elm Street)
Äs Nodt (Bleach), Sternritter "F", can amplify one's fear to lethal levels.
While kind and motherly on the surface, Retsu Unohana (Bleach), is one of the most feared Shinigami in all of Soul Society, even to those who are unaware of her true self.
Batman (DC Comics) is well known for his ability to inspire fear in others...
...to the extent that he was chosen as a candidate for the Sinestro Corps.
Parallax (DC Comics), the living embodiment of all fear.
Batman (DC Universe) under the influence of the Scarecrow's fear-inducing toxin.
Sinestro Corps (DC Comics)
Through the power of his sword, the Fright Knight (Danny Phantom) is able to send his victims to an alternate dimension where they are forced to experience their greatest fears.
Chaos (Sonic the Comic) possesses a powerful aura of fear that causes anyone in close proximity to him to become petrified with fear.
Boogeyman (Boogeyman 2)
Blackheart (Marvel Comics)
Ghost Rider (Marvel Comics)
Scarecrow (Marvel Comics)
Alexander Aaron (Marvel Comics)
Caliban (Marvel Comics)
Barbas, The Demon of Fear (Charmed) can literally scare people to death by bringing their fears to life.
The Fear (Metal Gear Solid 3: Snake Eater) truly lives up to his name.
Fear (Inside Out) is Riley's capacity to feel fear, making her feel fear whenever he's at the controls.
Kuudo Hinokage (Medaka Box) induces an intimidating presence so powerful people cast him out of conscious thought and cognitive perception.
It (Stephen King's It) in the form of Pennywise
In order to feed, The Jeggorabax Energy Entity (The Sarah Jane Adventures) induced fear into its victims
Huwawa (Valkyrie Crusade) terrifies all who see her eyes.
Darkrai (Pokémon) can inflict fear with its ability to make people see nightmares.
Fungus Humongus (Teenage Mutant Ninja Turtles;2012 Tv series) can produce hallucinatory spores which causes it's victims to experience their worst fears.
As the Emperor of Evil, Frieza (Dragon Ball), was the most feared mortal in Universe 7, to the point that even decades after his death his sheer fear factor was stated to be the only thing keeping his empire from collapsing.
The prisoners of level 6 (One Piece) have committed crimes so vile even the newspapers refused to write about them. The world fears the inmates to the point that the World Government has to “erase” their existences from history.
Charlotte "Big Mom" Linlin (One Piece) is a highly feared pirate with a fear factor so great that even the Giants do not dare speak her name.
Kaido's (One Piece) status as the "Strongest Creature in the World" makes him so feared that people would rather risk declaring war on the World Government than anger him.
Because of his sheer ruthlessness, Sakazuki (One Piece) is feared by both allies and enemies alike, including the dreaded Blackbeard Pirates.
As the chief enforcer of the Emperor's tyrannical will, Darth Vader (Star Wars) was one of the most feared beings in the galaxy.