An-Nisaa (The Women)

149. "If you do good openly or conceal it or pardon (others) evil, then verily Allah is All-Pardoning, All-Powerful."

Whenever you are in the position of power, and forgiveness has a training effect, do forgive; and wherever silence is abasement, and it strengthens injustice, do shout.

Therefore, vengeance and retaliation is 'legitimate', when remital and forgiveness is 'virtue'. So, it is worthy to pardon when you are powerful. It says:

"....then verily Allah is All-Pardoning, All-Powerful."

Imam Amir-ul-Mu'mineen Ali (as) says:

"When you gain power over your adversary, pardon him as gratitude for being able to overpower him."¹