In Spheres Of Might one of the Berserker talents is
Bloody Counter As an immediate action, when a creature targets you with a melee attack, before the attack roll is made you may allow the attack to automatically strike you (although the roll is still made to determine if the attack threatens a critical hit). After the damage is determined, you may make a brutal strike targeting that creature as a free action that may be taken even when it isn’t your turn, if it is in range. If the creature attacking you is battered, you may resolve your attack action prior to their attack being resolved.
If your attack kills them or pushes them out of their weapons range does it invalidate any damage they would have dealt?