Welcome to Smogon! Take a moment to read the Introduction to Smogon for a run-down on everything Smogon, and make sure you take some time to read the global rules.
Name: Flex-off
Power: 0
Accuracy: can't miss
PP: 15
Category: Status
Type: Fighting
Effect: The Pokémon with the higher attack stat gets a x2 boost to their attack and defense, stat boosts don't count, can't be used twice in the same switch in, single target
Priority: 0
Flags: Dance
Potential...
Name: Flex-off
Power: 0
Accuracy: can't miss
PP: 15
Category: Status
Type: Fighting
Effect: The Pokémon with the higher attack stat gets a x2 boost to their attack and defense, stat boosts don't count, can't be used twice in the same switch in, single target
Priority: 0
Flags: Dance
Potential...
I think it should be banned, because forcing Yveltal to be on every team to have a chance at beating it isn't fun. Every time Calyrex Shadow gets a knock out, it gets +1 to its 165 base special attack, making it destroy everything without a supereffective priority move, due to its speed.