* Typhon in GreekMythology, who likely doubles as the [[UrExample original]] HeroKiller, storming Olympus by himself and driving the gods into hiding. Hades was this to the Greeks themselves; he's the yardstick by which terrifying creatures in myth (like Typhon) are compared to. Typhon is so bad that he was not only scarier than Hades, he actually frightened him.
** He didn't just scare Hades; ''all of the Olympians were terrified of him''. When he first showed up to fight Zeus, all of the other Olympians except Athena and Enyo immediately fled in terror.
*** Athena helped her father. What did Enyo do? [[NightmareFetishist She]] stood and rejoiced wishing for the battle never to end.
* Jörmungandr and ''especially'' [[BigBadassWolf Fenrir]] in NorseMythology. When there's prophecies running around about how you're going to end the world you tend to get this.
** Odin the Allfather himself. A typical example of GoodIsNotNice and DarkIsNotEvil. Odin has over 200 recorded names and titles: Half of them are about what a [[NamesToRunFromRealFast scary guy Odin is]].
* [[GodOfEvil Apep]] in EgyptianMythology (who also goes by the name Apophis.) He was so terrifying, the Egyptians built temples to ''prevent'' him from coming to them. [[EldritchAbomination This was not undeserved]].