Marvel's Deadpool has garnered a lot of attention as a result of his amusing actions and absurd banter. Some of his most obscene and memorable actions include the time he stole Thanos' Infinity Gauntlet as well as the moment he gave up killing for non-violence. Because Deadpool has garnered a lot of attention, it's difficult to pinpoint his biggest fan. But in Cullen Bunn, Salva Espin, Veronica Gandini, and Joe Sabino's "Deadpool Killogy," Deadpool's biggest fan finally makes an appearance.
Deadpool's biggest fan in the Marvel Comics is a Watcher. In the Marvel Universe, the Watchers may possibly the oldest beings and are dedicated to extensive note-taking. As they observe everything that occurs throughout the universe, they document what they see and store that information. But the most pertinent rule the Watchers are not supposed to break is to never interfere. But in Bunn, Salva, Gandini, and Sabino's "Deadpool Killogy," the Watcher whose sole purpose is to observe every Deadpool in the Multiverse has no choice but to intervene.
After Dreadpool (one of Deadpool's darker counterparts) kills every hero in the Marvel Universe because he learns the truth that all of the characters in the MU are simply created for the amusement of the reader, he doesn't stop there. His next target becomes every Deadpool in the Multiverse. When Dreadpool begins wiping out countless versions of Deadpool including Headpool, Dogpool, as well as Golden Age Deadpool, the Deadpool Corps, a team of Deadpools dedicated to stopping Dreadpool recruit Deadpool from Earth-616 to help them. Because the Watcher becomes fed up with Dreadpool and the Evil Deadpool Corps slaughtering Deadpools throughout the Multiverse, he joins the Deadpool Corps. But it's not until Deadpool Kills Deadpool #3, does the Watcher officially join the fight. In the issue, the Evil Deadpool Corps - lead by a Frankenstein version of Deadpool called Evil Deadpool - confronts the Deadpool Corps at their HQ - which just so happens to be an amusement park. When the Deadpool Corps and Evil Deadpool Corps begin to fight each other to the death, the Watcher stands by and only watches because he doesn't know which side to choose - he loves every Deadpool in the Multiverse. But after his favorite Deadpool called Lady Deadpool sacrifices herself by flying the Deadpool Corps ship directly into Galactipool's face, he has a change of heart and decides to intervene.
Because the two remaining members of the Deadpool Corps - which are Deadpool from Earth-616 and Pandapool - have no way of reaching Dreadpool and the remaining members of the Evil Deadpool Corps, the Watcher teleports them to a nexus that will allow them to teleport to the world that Dreadpool inhabits. When they arrive at the Nexus, they realize it has been destroyed by the Evil Deadpool Corps. After Deadpool and Pandapool fight and kill Deadpool the Duck, the Deadpool Dinosaur, and D.E.A.D.P.O.O.L. in Deadpool Kills Deadpool #4, the Watcher sacrifices himself and uses the rest of his power to teleport Deadpool and Pandapool to the realm that is reigned over by Dreadpool.
Although there are a plethora of individuals in both the real world and Marvel Universe that are devoted fans of Deadpool, his biggest fan, the Watcher, was willing to break his number one rule, sacrifice himself to help Deadpool, and sacrifice himself to save the Multiverse. That's fandom taking to the extreme!