Commander

Whenever you lead a group action, gain +1 scale (for example, a small group counts as a medium group). If you lead a group action in combat, you may count multiple 6s from different rolls as a critical.

A group action is one where multiple PCs perform the same action and roll their respective pools for those actions (see Lead a Group Action, page 158). If you already have scale on your opponent, you gain an additional scale (and therefore level of effect). If two or more players roll a 6, then the result of the roll for everyone is a crit. You must still suffer stress costs from any participant whose result is a 1-3.