The Justice League has faced countless villains, but only a few have managed to make an unforgettable first impression. From galaxy-threatening entities to devious masterminds, these debutants proved to be a formidable challenge for the Earth’s mightiest heroes. Here’s a look at the 11 best villain debuts in Justice League history.

1. Darkseid: With his first appearance in “Superman’s Pal Jimmy Olsen” #134 before facing off against the League, Darkseid’s god-like powers and tyrannical rule over Apokolips instantly established him as a major threat.

2. Brainiac: Making his entry in “Action Comics” #242, Brainiac’s unmatched intellect and prowess for technology has made him an enduring foe for the League, repeatedly challenging them to thwart his schemes.

3. The Anti-Monitor: This villain debuted during the “Crisis on Infinite Earths,” posing such an existential threat that it required the collective effort of all heroes across the multiverse to stand against him.

4. Lex Luthor: Traditionally Superman’s arch-nemesis, Lex Luthor became a prime adversary for the entire Justice League with his brilliant but warped mind dedicated to humanity’s supremacy – or rather, his own.

5. Sinestro: Formerly a Green Lantern himself before appearing as a villain, Sinestro’s knowledge of the Corps and his ability to instill great fear made his debut confronting the Justice League memorable and chilling.

6. Starro the Conqueror: This mind-controlling alien starfish was actually the very first foe faced by the original Justice League of America in “Brave and The Bold” #28, marking an iconic entrance that has kept Starro relevant for decades.

7. Doomsday: Bursting onto the scene in “Superman: The Man of Steel” #17, Doomsday is best known for being one of the few villains who could – and did – kill Superman, forcing the League to reassess their approach to such unstoppable threats.

8. Black Adam: Originally a rival to Captain Marvel/Shazam, Black Adam’s overwhelming power and ruthless ancient Egyptian morality brought him into direct conflict with the Justice League on many occasions after his reinvention as an anti-hero/villain.

9. The Crime Syndicate: Debuting on “Justice League of America” #29, this group of evil doppelgängers from an alternate Earth showcased what happens when power is unchecked and absolute, presenting a dark mirror to our heroes.

10. Despero: Introduced in “Justice League of America” #1, Despero quickly became one of the most powerful foes with psychic abilities and physical prowess that challenge even the strongest members of the Justice League.

11. Prometheus: Appearing in “New Year’s Evil: Prometheus” #1 as a dark counterpart to Batman, he was crafted as an antithesis to justice; an embodiment of vengeance against good who meticulously planned his moves against heroes.

These memorable villains have defined what it means to challenge justice itself and have proven time and again why they are considered some of the greatest adversaries ever faced by the Justice League.