Activator MOB_DAMAGE

MOB_DAMAGE is executing when player left-clicking or shooting mob. You can define mob type (name supported too) and item (in player's hand) for this activators

/react add MOB_DAMAGE <ActivatorId> type:<MobType> name:<MobName> [item:<Item>]

Example:

/react add MOB_DAMAGE SuperCowKill name:{&6Super Cow} type:COW item:{type:STICK}

Temporary placeholders provided by this activator

PlaceholderDescription
%moblocation%Location of mob
%mobtype%Mob type.
If you using Citizens plugins - NPC will have type "PLAYER"
%mobname%Mob name.
If mob has no custom name this placeholder will be equal to mob type
%mobdamager%Player who hitting mob
%damage%Damage the will deal to mob. You can modify this temporary variable using VAR_TEMP_SET action to change value of mob damage