I like this definition:
Compassionate treatment, especially of those under one’s power; clemency.
A disposition to be kind and forgiving: a heart full of mercy.
Something for which to be thankful; a blessing: It was a mercy that no one was hurt.
Alleviation of distress; relief: Taking in the refugees was an act of mercy.
~from Old French merci

This original painting is dear to me and available now for sale in my shop!