Avengers Forever is a twelve-issue comic book limited series serialized by Marvel Comics from 1998 to 2000 starring the superhero team called the Avengers. The series won the R.A.C. Squiddy Award for Best Limited Comic Series in 1999 as well as the CBG Award for Favorite Limited Series in 2000.
The story revolves around the "Destiny War", a time travel-based conflict between Kang the Conqueror and his future self, Immortus. Notably, the story effectively comes to a complete halt in issues #7 and #8, as Busiek uses these issues to iron out the many wrinkles in Avengers history and clarify the history of Kang in explicit, flashback-filled detail, in turn undoing much of the poorly-received Avengers: The Crossing crossover from a few years prior.
You can find Avengers The Crossing Crossover here: