Excalibur has reunited and wants revenge on the Avengers because of the AvX events. They attack the Avengers while they are enjoying their annual picnic at Central Park. Avengers get a four minute heads up. All current versions (including Thor and Vision)
Round 1: Morals on. Both sides seek to humiliate the other.
Round 2: Morals off. Both sides seek to kill each other.