Board Thread:Question and Answer/@comment-67.129.66.62-20161014202756/@comment-25151790-20161014215810

The Ace is the first player to deal the most damage to an Archwitch before it is defeated, not counting overkill. Your damage isn't counted until you tap past the "Victory" screen, are defeated, or flee.

Here are some examples:
 * P1 and P2 start at the same time and both deal 60% damage, but P2 finishes first.
 * Result: P1 - 40%, P2 - 60% (Ace)
 * P1 and P2 start at the same time. P1 deals 51% damage and flees before P2 finishes. P2 deals 500% damage.
 * Result: P1 - 51% (Ace), P2 49%
 * P1 starts first, dealing 40% damage before being defeated. P2 and P3 join in afterwards with 60% left. P2 deals 30% damage and is defeated before P3 finishes. P3 deals 60% damage, finishing off the AW.
 * Result: P1 - 40% (Ace), P2 - 30%, P3 - 30%