56 years ago - Slade Wilson is born.
40 years ago - 16-year-old Slade lies about his age to join the Army.
37 years ago - 19-year-old Slade is accepted into an elite operative unit.
31 years ago - 25-year-old Slade is promoted to lieutenant commander under Adeline Kane.
29 years ago - 27-year-old Slade's superior officer Adeline Kane gives birth to his son Grant Wilson.
27 years ago - 29-year-old Slade's superior officer Adeline Kane gives birth to his second son Joseph Wilson.
25 years ago - 31-year-old Slade is selected to join the elite covert ops unit Team 7. He often becomes combat partners with Patricia Trayce.
23 years ago - 33-year-old Slade is the subject of an military experiment that enhances his mental capacity after Team 7 is shut down.. He hides the results & leaves the service to become a mercenary.
20 years ago - 36-year-old Slade rescues his son Joseph Wilson from kidnappers, but his throat is cut during the process. Adeline shoots him for jeopardizing their child, costing him his eye.
19 years ago - 37-year-old Slade first works with Patricia Trayce, as she becomes a mercenary, their relationship equal parts rivalry, partnership and romance.
17 years ago - 39-year-old Slade has an affair with Greenpeace aid worker Lillian Worth who hides her pregnancy & gives birth to Rose Worth.
12 years ago - 44-year-old Slade competes for Carmine Falcone's 50 million dollar bounty on Batman. Floyd Lawton kills Patricia Trayce, making himself a rival to Slade.
10 years ago - 46-year-old Slade is barely stopped from taking out the Teen Titans after Grant dies fighting them, his HIVE implants overloading his nervous system. He meets Terra Markov, a fellow mercenary, and begins a relationship with her.
8 years ago - 48-year-old Slade attacks the Teen Titans through Terra Markov. he is stopped by Joseph Wilson, who he is forced to kill.
6 years ago - 50-year-old Slade discovers his daughter Rose Wilson & kidnaps her, beginning her training as an assassin.
3 years ago - 53-year-old Slade & Rose Wilson fight the new Teen Titans. He shoots Bart Allen in the knee with a shotgun.
2 years ago - 54-year-old Slade is hired to attack the Justice League by the Calculator, almost taking them all out.
1 year ago - 55-year-old Slade realizes that Rose Wilson is becoming dangerously unstable when she cuts out her own eye. He abandons her.
There are bigger villains in the DC pantheon. Some of the biggest bad-guy archetypes in ALL of fiction are in there; the Joker and Lex Luthor are huge. But there's a very real reason that Deathstroke is the very first villain we've incorporated into our timeline. This guy is absolutely everywhere. He was introduced as a Teen Titans villain, but over the years he's fought almost everyone, because it's hard to argue with the level of quality in this character.
While he has made minor appearances in a few different books as a SLIGHTLY heroic character (most notably in the Panic in the Sky miniseries, where he led the ground forces against Brainiac's invasion), For the most part he's been allowed to stay a villain, which is a tricky feat for a character that so thoroughly captures the collective audience's imagination. He's recurred consistently across the entire history of the Teen Titans, become a major Batman villain, battled the entire Justice League to a standstill, and is universally recognized as the preeminent assassin in the entire DC Universe.
He's a central linchpin to several wider story arcs similar to Batman and Superman. He's THAT big a character, and his role just keeps expanding.