Batman vs the Joker
I remember being blown away by how epic this fight felt. The whole book was leading up to it, then when they stare each other down in front of Commissioner Gordon at the Joker’s demented funhouse right before they’re about to battle… That’s everything that’s great about comics.
Darkseid vs Green Arrow and the Atom
I loved this, because Grant Morrison had teased it in an issue of Wizard magazine months before it ever happened. He said something along the lines of “It all comes down to Green Arrow and the Atom alone against Darkseid, and they win!” So for months, my mind struggled with how they could possibly do that. To see it happen was a thing of beauty.
Superman vs Thor
This was 1/2 DC, so I think it counts. I’m a huge Superman fan, so this one was personally gratifying to see, especially since issue one ended on a big splash page of Superman being smacked by Mjlonir.