็Have little question

I want to make this Ability.

Penitence [Name of Ability]

taking more damage from attacks or spells.
this spell same DotA

I don't know how to create it, plz tell me for make it.

Berserk.

ahhhh, berserk for self I want to make skill use to target single enemy.

use trigger to give berserk on targeted enemy and order enemy to cast it, remove berserk after that

if target has player? it cast berserk but he see berserk skill i think it not good.

Trigger it. Create a trigger with the '[Target unit of ability being cast] takes damage' and damage him again for a % of GetEventDamage.

Huh? have trigger getdamage %? I can't see that, I want to make skill same DotA - -", someone can help me?

I want this trigger very much T-T Plz help me.

i think, what blu means is, that you for example store the target unit in a game cache and then check, when it is attacke, if it has a specific value, if it has then you order the attacking unit to deal the % dmg towards the target unit.
You could also make it with a buff, but i personally don't like buff anymore.
---Edit---
And you don't want berserk, so you have to trigger it.
When you want the trigger try it first yourself, else you won't ever learn anything.

Fireeye, no, that isn't what blu means. You'd use a dynamic trigger to get when it is damaged, then cause extra damage when it happens.