Dick Grayson has been around since the Golden Age of comic books. He began as the first sidekick in comic book history before evolving into his own hero, adopting the Nightwing persona during his tenure with the New Teen Titans. Around this time, he also met Slade Wilson, and the two engaged in a rivalry that would go on for decades.
Still, despite their blatant hatred for each other, Dick and Slade have a more complex relationship than anyone imagines. They have even teamed up at times, albeit reluctantly, giving more nuance to their dynamic. And while mainstream audiences might know the basics about their rivalry, comic book fans know the specifics.
The Judas Contract
Many fans know the basics of the Judas Contract storyline. Deathstroke signs a contract for H.I.V.E. to destroy the Teen Titans and uses Terra to infiltrate the team. However, the story is also a landmark in Dick and Slade's careers.
During these events, Dick formally becomes Nightwing, forever leaving the Robin identity behind. Furthermore, The Judas Contract is the only commitment that Deathstroke has ever failed to fulfill. Dick and Slade met at pivotal moments in their lives, providing further understanding for their animosity. For Dick, Slade is the first villain he faces during his mature stage as a bonafide leader, becoming an archenemy of sorts. For Slade, Dick represents the failure of his career, a resentment that later evolves into respect.
Dick Was Friends With Slade's Son
Before the New 52 continuity, Slade has three children, Grant, Joseph, and Rose. Grant dies while fulfilling the original Judas Contract, prompting Slade to take it to honor his son, and Rose comes into the picture until much later, but Joseph actually joins the Teen Titans under the name Jericho.
The rest of the team mistrusts Jericho because of Terra's recent betrayal, so Dick takes him under his wing. He eventually becomes one of the most powerful members of the Teen Titans, until the infamous Titans Hunt storyline, where Jericho descends into insanity after being corrupted by Azarath's soul and Trigon's essence. Dick and Slade join forces to locate him, finding him in a state of severe mental stress. Jericho convinces his father to end his suffering, and Slade reluctantly kills him.
Dick Trains Slade's Daughter
Comic book fans know Dick Grayson adopted several identities over the years. Among them was Renegade, a moniker he took while trying to infiltrate Lex Luthor's Society of Super-Villains. As part of his cover, Dick trained Slade's daughter, Rose, AKA Ravager.
Wilson didn't wholly trust Dick, so he kept a close eye on the training. However, the two strike an understanding during this time, taking their relationship from frail rivalry into frenemies territory and cementing their mutual respect. Things turn sour when Slade discovers Dick taught Rose about the nature of heroism. Furious, Slade strikes a reluctant deal with Dick, promising to leave Blüdhaven out of the Society's plans if Dick stops training Rose.
Slade Destroys Blüdhaven
Wilson's anger at Dick's betrayal prompts him to go back on their deal. Under the order of Alexander Luthor Jr., Slade took several other villains to Blüdhaven to drop Chemo, one of the best monsters in DC comics, into the unsuspecting city.
By that point, Chemo was but a pile of radioactivity, nearly deprived of any brain function. The explosion killed thousands and effectively destroyed Blüdhaven, with Slade explaining that Dick needed to feel abandoned and unable to ever return home. The act forever turned the tables on their relationship, breaking any chance for redemption between the two and establishing them as mortal enemies.
Slade Forms The Teen Titans East
After Batman and Nightwing defeat Slade during the climactic battle of Metropolis at the end of Infinite Crisis, he reappears in One Year Later. Seemingly planning to "reclaim" Ravager and take his revenge on Dick, he forms the Teen Titans East, selecting each member to counter the current Teen Titans line-up.
Things came to an end when Slade launched his attack against the Teen Titans. Dick, leading a team of former Titans, also joined the battle, eventually defeating Slade, who escaped aided by Inertia. However, Slade's real plan was always to cement Ravager's place within the Titans and successfully reinstate the newly-resurrected Jericho into the team, thus giving them the family he could never provide.
Slade Uses Damian To Try And Kill Dick
Despite making his peace with Rose's choice to be a hero, Slade's hatred for Dick remained. Deathstroke has a long history with the deathly and infamous League of Assassins, acting as their enforcer numerous times. During the Return of Bruce Wayne storyline, Slade and Talia al Ghul implant a mind-controlling device on Damian Wayne's back, effectively taking over his body.
Slade then uses Robin to try and kill Dick, who was acting as Batman at the time. However, the stress proves too much for Damian's mind, allowing Dick to gain the upper hand. The encounter leaves Slade heavily injured and at the hospital, where he receives a visit from Dick. The two confirm their hatred for each other, with Dick declaring that he'd be back to take his vengeance for Blüdhaven's destruction.
Dick Sees Slade As Batman's Dark Reflection
Everyone knows Dick's greatest fear is to become Batman. He actively works to step out from under the Dark Knight's shadow, carving a persona of his own that stands in stark contrast to Batman. Indeed, Nightwing learned many things from Batman, but he's terrified of becoming him.
Dick's fears explain his enduring animosity towards Deathstroke. Slade is the personification of Bruce's darkest impulses: he's selfish, secretive, manipulative, uncaring, controlling, overly ambitious, and exceptionally gifted. Whenever Dick fights Slade, he's also fighting Bruce's most toxic nature, and in a way, his own.
Slade Could Kill Dick If He Wanted
Many characters in the DC universe consider Deathstroke to be the most dangerous and effective assassin in the world. His skill is unrivaled, to the point where R'as al Ghul considers him a worthy candidate to take over the League of Assassins.
Throughout his many battles with Nightwing over the years, Deathstroke always has the upper hand. It's apparent that, should he want to, he could finish the job and kill Dick, although he never does. Instead, Dick keeps training and improving, becoming more proficient every time they meet. Perhaps they'll one day come to a point where Dick defeats Slade; alas, that day is yet to come.
Slade Deems Dick A Worthy Successor
Despite their many clashes and differences, Slade shows great respect for Dick's abilities. Like other of Nightwing's deadliest adversaries, like Lady Shiva or Talon, Slade acknowledges Dick as a master combatant and worthy rival. In fact, the comics hint numerous times that Slade might consider Dick the only worthy successor to the Deathstroke mantle, even more than his own children.
Slade's ambitions finally come to pass in the current Future State storyline, where Dick adopts the Deathstroke persona, vowing to get the job done "no matter what it takes." The mask features elements from both Deathstroke and Nightwing, a symbolic representation of their dynamic as a whole. Dick and Slade's relationship keeps changing and evolving even after all these years, cementing it as one of the best rivalries in DC comics.