2024's Deadpool and Wolverine was a huge blockbuster built on the team up of the two title characters. And though they wound up leading a group of outcasts in the Void, that might be about as close as Deadpool actually gets to actually being on a team, as the Merc With a Mouth himself Ryan Reynolds says joining the Avengers or X-Men would be "the end" of the character.
Indeed, Deadpool's quest to become an Avenger was central to the plot of Deadpool and Wolverine, though it seems that's a dream that won't necessarily come true despite Wade Wilson saving reality.
