The What If? Festival, Part IX: What If? Annihilation.

Or: What if the Annihilation Wave reached Earth in the middle of Civil War?

Or: What if Civil War ended the way it was supposed to?

Nova convinces the heroes to drop their political differences for five minutes to handle this direct threat to all life on the planet. Unfortunately, the conclusion is reached that a few may have to sacrifice their lives to ensure that their last ditch solution works the way it's supposed to. Who volunteers? I'll give you one guess:

You saw that coming, right? Please tell me you saw that coming!

So yeah: Tony and Steve decide to go down together for the sake of humanity. And before their final battle, they make peace. Like I said, this is how Civil War should've ended: