Criteria: Cards that destroy, exile, shuffle, give -X/-X, or deal more than one damage to all creatures or permanents, but possess some sort of caveat when they do so that could reasonably be built around, or specify that only opponents do so
If the spell instructs another object to deal damage, its controller won't gain life when that damage is dealt
The double black can be a pain, but this is still premium
Nimble Obstructionist prevents effects activated or triggered abilities, and Teferi, Mage of Zhalfir has a static effect that changes all opponents' spells to sorcery-speed Removals are important for dealing with dangerous permanents or STAX pieces, strategy based on disruption, taxes and resource constraints
Perhaps theyre only very well tied up, as in The Binding of the Titans
Paying five mana to create a rat creature token for each opponent you have is expensive, but in Commander, that could be up to three