A common question about ICONS is its lack of an initiative system although, technically, it does have one:
“Typically, the conflict starts off with the panels of whichever side initiates: if a villain launches an attack, start with the villain’s panel. If the heroes spring into action, begin with their panels. Once one side’s actions are resolved, go to the other side, then back and forth until the conflict ends.”
— Conflict, ICONS Superpowered Roleplaying, page 55
So, there’s no system for it other than “Whoever goes first, goes first.” Usually, that will be fairly obvious. In situations where it is not, or if a group prefers a more detailed or mechanical initiative system, here are some options:
Steve Kenson 