Moon Knight may be popular in large part due to their memorable heroes, but no hero can flourish without notable villains. Villains are essential to comics as their evil actions are what really get readers to keep reading to see what monstrosities they will do next.
Most heroes have groups of well-known villains, and the bigger the group and the bigger the impact made by these villains, the more they stick in fans' minds. Even though heroes are meant to be the ones that are cheered for, a lot of them end up getting a large group of villains that want nothing more than to see them dead with large portions of these villains becoming fan favorites.
Spider-Man
This friendly neighborhood hero can't help but get himself in trouble with his big mouth shooting constant insults. Despite being a street-level character, his rogues' gallery is fairly diverse, including scientists such as Dr. Octopus, Lizard, Morbius, and Green Goblin (whose something of a scientist himself) and street criminals like Rhino, Mysterio, Sandman, Electro, and Scorpion.
Each of these villains hates Spider-Man and frequently forces to form groups like the Sinister or Savage Six (though the groups' rosters are constantly in flux). Luckily, Peter Parker does have some villains that serve as allies at times such as Venom and Black Cat. Some of the Kraven the Hunter next on the slate.
Wonder Woman
Leader of warrior women known as the Amazons, Wonder Woman is no stranger to combat. This is often challenged as her biggest threats such as the master of the hunt Cheata and the God of War Aries are also skilled in combat and battle strategy. Her opponents come in all shapes and sizes as evidenced by the telepathic Doctor Psycho and the giant Giganta.
In addition to visual differences, Wonder Woman's villains also boast a wide range of powers and abilities. For example, Silver Swan has flight, Circi can turn men into animals, Doctor Cyber has cybernetic abilities, and the deadly Dr. Poison stays true to her name.
Green Lantern
With rings that can create anything imagined, the Green Lantern Corps uses willpower with other lantern corps using different colors representing different emotions. Some Lantern Corps are allies such as the Blue Lantern representing hope and at times the Star Sapphires, including Hal Jordan's girlfriend Carol Danvers, representing love.
Many of the coolest Green Lantern villains lead their own Lantern Corps. When guarding Earth, the lanterns protect people from threats like Hector Hammond, Doctor Polaris, and the man that uses tattoos as a weapon, Able Tarrant. The biggest threats are the ones that require multiple Lanterns to stop, such as the likes of Atrocious, Larfleeze, and Hal's arch-nemesis, Sinestro. The Lantern's villains are sometimes strong enough to end the universe, as proven through Black Lantern Nekron during the Blackest Day event.
Aquaman
Once considered a joke character, Aquaman has grown into a hero taken seriously in large part due to some interesting villains. One of Aquaman's major villains is Ocean Master, and, while the "evil brother" plot device may seem overdone, his stories highlight the familial struggles that Arthur Curry has dealt with his whole life.
Aquaman also goes against threats with sharp teeth like King Shark and the terrifying sea creatures known as The Trench. Despite all of these intimidating foes, his most dangerous villain is the revenge-driven Black Manta, who has often succeeded in taking away Aquaman's happiness by attacking his relationship with Aquaman's wife, Mera.
Superman
Superman may be one of the strongest heroes in comics, but most of his villains have been custom-made to give him a challenge anyway. Notable enemies that were created as an inversion to the Man of Steel include Cyborg Superman, Metallo, Bizzaro, and, the first to succeed in killing Superman, Doomsday.
Superman's powers and strength even set him up as a target for leaders of other planets including Darkside's Apokolips, Mogul's Warworld, and what is left of Krypton (led by General Zod). When not going against villains that enjoy chaos such as Toyman and Lobo, Superman would have to protect the world from some of the smartest supervillains in Brainiac and the infamous Lex Luthor. The incredible power levels and diversity in Superman's villains make them more memorable than most others.
Fantastic Four
Not only does the Fantastic Four have the best female villains, but some of Marvel's current heroes even started off against the first family as villains. The likes of Silver Surfer, Namor, and the Inhumans all found themselves at odds with the Fantastic Four before finding their more heroic sides.
The threats that they face are on a cosmic level, and they often go against space invaders the likes of Negative Zone's Annihlus, Super- Skrull, and the eater of worlds, Galactus. Their biggest, most constant threat, however, is the diabolical Dr. Doom, who mixes a twisted sense of patriotism and duty with his incredibly mystic and technological know-how to threaten the freedom of everyone on Earth.
Daredevil
The protector of Hell's Kitchen has his own hell to fight as he battles groups of enemies who want him dead. Despite starting off with some more theatrical villains such as Jester, Matador, and Stilt-Man, Matt Murdock eventually grew into a grittier character with more serious foes to fight.
Most notably, Kingpin has power and control over parts of New York that brings out the blind lawyer's gritty side and tests his limits. Kingpin's war on Daredevil brings in more villains for the hero as the mercenary that can turn anything into a weapon Bullseye is often the one hired to kill Daredevil. With the mystic ninjas in The Hand also added into the mix, Murdock's foes are entertainingly diverse and dangerous.
X-Men
At times, the X-Men can be darker than their villains, but it is Magneto who channels the dark side of all mutants as he forms the Brotherhood of Evil Mutants. Enlisting Mystique, Toad, Juggernaut, and Sabbertooth to oppose Professor X's peaceful approach to gaining mutant equality, Magneto showcases an aggressive (if not partially understandable) philosophy of survival.
Those in the Brotherhood aren't the only notable X-Men villains, however. Mutants often find themselves at odds with humanity, and people like Bolivar Trask have gone as far as deg the mutant-hunting Sentinals. These towering, mechanical terrors showcase the interesting thematic clashes that draw parallels between mutants and certain real-world struggles.
The Flash
The Flash's rogue's gallery is interesting because it's a mix of villains that are evil for evil's sake and those that are simply trying to survive. Some of Flash's villains share his powers, including Black Flash, Jonny Quick, God Speed, and Reverse-Flash. These enemies are memorable for shining a light on who Flash could've if his heart wasn't so heroic.
Other groups of villains, The Rogues, are more grounded in their goals and sometimes even have a good rapport with The Flash. Led by Captain Cold, Golden Glider, Heat Wave, Pied Piper, Mirror Master, Trickster, and Weather Wizard, The Rogues, have all made an agreement to not kill women or children and to not kill a speedster. While this is hardly a noble set of guidelines, it's more than most villains do to curb their carnage.
Batman
Batman wouldn't be the hero that he is without his rogues' gallery and their diverse motives. Harley and Mr. Freeze do evil for others; Killer Croc and Scarecrow do it for fear; and others such as Clayface, Madhatter, and Two-Face cause chaos after losing their sense of self. While each of these villains is detailed in their own right, they've become fan favorites due to the way in which they hold a mirror up to Bruce's own internal struggles.
While the "A-List" villains get most of the spotlight, even the less-commonly-seen enemies are given time to shine in famous stories like The Long Halloween and Batman: Year One. While Batman himself does a lot to ground the city of Gotham, it's his wide range of foes that have kept him popular for decades across several mediums of entertainment.
