FAQ: How do I detect whether a player is critically hitting in vanilla MC?

This question if most commonly asked because many server admins feel that critical hits are imbalanced. If you have other plugins that interfere, then this is a potentially sticky problem - however, for vanilla MC other than MD, the following solution would be effective:

Damage:
    - 'if attacker.type.player and attacker.isfalling':
         - '-1'
         - 'mult.2'
         - 'div.2'

The reason that this works is because vanilla MC grants crits to all players who have a downward velocity - thus, the usage of the Falling conditional. The mechanic is countered as it is described according to the MinecraftWiki page located here.