If a model with the Curse is removed from play, then the enemy unit responsible, by inflicting the final wound for example, will immediately suffer D6 S 5 hits (if the model was a Lord) or D6 S 4 hits (if the model was a Hero). These Wounds are distributed as for shooting hits.
In close combat, any Wounds inflicted count towards the combat result. If more than one unit is responsible for the destruction of the model with the Curse (it is destroyed by the combat result in a multiple combat due to Unstable, for example), then all guilty units are affected. If the model is killed in a challenge, then only his opponent is cursed, and not the whole enemy unit.