Solved Extra Rocket Damage

[LeeifMR]

Any way to make it so when a certain player shoots a firework rocket from a crossbow it does extra damage? I tried using metadata tags but I couldn't figure it out

 

[HeliumBoi]

Any way to make it so when a certain player shoots a firework rocket from a crossbow it does extra damage? I tried using metadata tags but I couldn't figure it out

I'm having difficulty figuring out what you mean by specific. You mean a player with a specific username, or someone with permission?
Regardless, there is what I could do:

on damage:
    if attacker is a player:
        if damage cause is entity explosion:
            if attacker has permission "rocket.damage.increase":
                set damage to damage * 2
                send "&cYou dealt %damage% damage to %victim%!" to attacker #damage indicator, you can turn it off if u want.