When you set this scheme in motion, each opponent chooses a creature they control, then sacrifices the rest.
All of the other creatures are sacrificed simultaneously after the opposing team chooses which creatures to keep.
If an opponent controls no creatures, that player isn’t affected by this scheme.
In a Supervillain Rumble game, first the next player in turn order chooses a creature, then each other opponent in turn order does the same. Then the other creatures are sacrificed simultaneously.