With two highly successful movies to his name, Deadpool has become one of Marvel Comics' most popular characters. This was not always the case, though. Despite occasionally crossing paths with the publisher's more established heroes, Wade Wilson's early adventures mostly occupied their own cartoonish corner of the Marvel Universe.
While he battled and began rivalries with an odd assortment of the villains of other heroes, Deadpool also collected a rogues gallery of his own. Some of Deadpool's enemies are amongst Marvel's most feared and powerful villains. Others, however, are completely ridiculous.
Ajax
The assistant of Doctor Killebrew, who himself was one of the scientists involved in the experiments that resulted in Wade's powers, Ajax, then known as Francis, was seemingly killed during Deadpool's initial escape from the facility. Returning years later rebuilt as a cyborg, he began systematically exterminating all former subjects of the Weapon X project, naturally bringing him into conflict with Deadpool once again.
In addition to his cybernetic enhancements, Ajax also possesses enhanced strength and reflexes, as well as a complete lack of sensitivity in his nerve-endings, rendering him immune to pain. Ridiculously overpowered, Ajax has still never been more than a nuisance to Wade in any of their many conflicts.
Doctor Bong
Originally the nemesis of one of Marvel's other misfit heroes, Howard the Duck, Doctor Bong is a brilliant scientist, who also wears a helmet designed to look and function as a giant bell, which he "rings" by striking with the large metal ball that replaces his severed left hand.
A master in the field of sonics, he has utilized the generated "BONG" caused by this action to a variety of effects, including forcefields, paralyzing attacks, and somehow, teleportation. Despite his vast scientific knowledge, and an array of Doctor Moreau-inspired mutant animal minions, Bong has been easily defeated by Deadpool in each of their encounters, including one instance in which Deadpool severed Bong's ball hand, rendering him effectively powerless.
Slayback
Gregory Terraerton was initially another Weapon X operative who was killed by Wade Wilson early in his mercenary career. Resurrected as a half-cyborg zombie, Terraerton took on the name Slayback and set out upon a campaign of revenge. It was later revealed that Slayback possesses a healing factor of his own, albeit a significantly slower one than Deadpool or Wolverine, but still allowing him to return from seeming death on multiple occasions.
With telescopic, razor-taloned arms and an increasingly zombified appearance, Slayback is one of Deadpool's most visibly unique recurring foes, with a polarizing look that has been both praised and mocked by creators and fans.
T-Ray
A man who believes himself to be the true Wade Wilson, T-Ray has been a reoccurring enemy of Deadpool since his first ongoing series. Claiming that Deadpool usurped his identity after leaving him for dead, (an event that Deadpool himself has a drastically different recollection of) T-Ray went on to study the mystic arts, transforming himself into a vastly powerful being.
In addition to his hulking strength and sorcery, he once even possesses a magical blade that was capable of nullifying Deadpool's healing factor, coming very close to killing him. Despite all of this, he sports one of comics' most ridiculous and laughable physical appearances.
Madcap
Driven mad after being the sole survivor of a bus crash turned chemical spill, the man who would become Madcap is not necessarily evil, like most of Deadpool's enemies. Rather, Madcap is best described as "chaotic neutral," a nihilist who deems all things, including existence itself pointless. When Madcap and Deadpool ran afoul of Thor, a lightning bolt reduced them to a pile of ash, where their combined healing factors reconstituted Deadpool with Madcap trapped as an often disagreeable voice inside his head.
When the two were separated, Madcap was driven further insane by his experiences trapped within Deadpool's mind and set out to destroy him. Essentially a living cartoon character, Madcap feels no pain, is completely impervious to injury and regenerates from even disintegration. Due to his madness, however, he also easily loses sight of his initial objectives, often quickly becoming bored in the midst of his actions.
Black Swan
A telepathic mercenary whose most prolific assassination was credited to Deadpool, Black Swan retaliated this blow to his reputation by kidnapping Deadpool and continually torturing him, preventing him from ever fully healing. When Deadpool eventually escaped, he tracked Swan down to his Bavarian castle, where both were seemingly killed in an explosion.
Through a complicated mix of telepathy and healing factors intertwining, the two both survived, in the process also leading to the creation of the Deadpool doppelgänger Agent X. With his fancy suits, an enormous fortune, and castle fortress, Black Swan is very much a stereotypical "mustache-twirling" supervillain, though he lacks the requisite mustache.
Juggernaut
Coming into conflict with Deadpool when the mercenary had a bounty out on his head, Juggernaut attempted to cash in, thinking it would be a quick payday. Unfortunately for the classic X-Men villain, he underestimated Wade's cunning, unpredictability, and incredible healing abilities. The two have maintained a strong disdain for each other since this initial encounter.
As one of the X-Men's most popular enemies, the Juggernaut is a step above the ranks of Deadpool's more personalized antagonists. Nearly indestructible physically, the Juggernaut has nevertheless taken massive bruising to his ego due to incessant banter of "the merc with the mouth."
Taskmaster
A recurring rival of Deadpool's, Taskmaster is a mercenary with photographic reflexes, allowing him to mimic the fighting styles of anybody whom he's seen. This has made him a formidable threat against heroes such as The Avengers and Spider-Man. Deadpool's unorthodox and unpredictable fighting style, however, has made him one of the few heroes Taskmaster has had trouble mimicking. The two mercenaries are frequent adversaries, yet occasional allies, their similar motivations bringing them into conflict just as frequently as in a partnership.
Taskmaster has had numerous costume designs throughout the years, with some definitely more threatening in appearance than others, but always wearing a skull on his mask. What could have been an instant credibility killer instead, combined with his deadly abilities and mysterious past, have managed to take Taskmaster from potentially corny to undeniably cool.
Evil Deadpool
A lovestruck scientist obsessed with Deadpool spent years collecting his severed body parts after his battles, storing them in her refrigerator. When Wade confronted her, she killed herself, and he discarded his old parts into a dumpster, where his healing factor merged the thawing parts into a deranged duplicate of himself.
With the same unhinged attitude and unpredictable streak as his progenitor, Evil Deadpool began a demented game of cat and mouse with the original, running in circles as each was able to anticipate the actions of the other. More insane and deformed than Wade himself, Evil Deadpool possesses all of the same powers and abilities, as well as, hilariously, two right arms.
Thanos
One of the biggest threats in the entire Marvel Universe, Thanos has a deep resentment and hatred towards Deadpool, due to Wade's unique relationship with the cosmic embodiment of Death, whom Thanos has long pined for the affections of. Even while not in possession of the Infinity Gauntlet, Thanos' massive size and strength, and a vast array of cosmic powers and weaponry made his conflict with Deadpool an obviously one-sided affair.
Still, with the fate of the universe in the balance, Wade stepped up to the challenge, eventually coming into possession of the uni-power, which temporarily imbued him with the powers of Captain Universe. With cosmic powers of his own, Deadpool was able to defeat the Mad Titan one on one, making him one of the few Marvel characters ever to do so, but cementing for himself a rivalry with one of Marvel's most dangerous beings.