Most of Mythic Mutants and some others have this ability.
"Target has it's next attack reduced by a percentage of the damage it just received. Doesn't Stack"
- NOTE: while it says "doesn't stack" on the ability tooltip, the tooltip of the debuff says "stacks to 5". The effect actually stacks to 5.
Most mutants with Curse have it start at level 4 at 20%, then increase to 30% at Level 25. A rank 3 Curse Orb gives 20%. A rank 4 ability orb can add 22% to either version of the ability.
Reduces the target's next attack by a flat amount. For example: If the user hit an opponent for 10,000 damage their next attack will be reduces by 2,000 damage(or to 0 if the Curse is more powerful than their damage), before taking gene weaknesses and resistances into account. So if they would have dealt 1,500, they deal 0. But if they would have dealt 10,000, they deal 8,000. This is taken into consideration before applying the bonus from the Boost ability. Example: 10,000 base damage - 2,000 for curse is 8,000, then factor in the bonus for Boost.
This benefits from attack orbs and critical orbs since it's based on the actual damage dealt by the attack, getting a critical hit means that the user inflicted a Curse of that magnitude.