mercy

Noun

(uncountable) Mercy is the quality of kindness and forgiveness that stops you from harming or punishing somebody who you could harm or punish.
- Synonyms: compassion, charity, pity and forgiveness
- Antonym: cruelty
The king would always prefer to show mercy, even to his enemies.

Please, sir, have mercy on an old man.
(countable) A mercy is a situation that it makes you feel lucky, usually because something worse didn't happen.
- Synonym: blessing
It was a small mercy that the storm didn't last long.
A mercy mission or journey is one to help people who are in great need.
They took food and set out on a mercy mission to find survivors.
If you are at the mercy of somebody or something, you have no control over your situation.
I hope the trip will be nice, but we're at the mercy of the weather.

You use mercy or mercy me to show surprise.
Mercy! You haven't come here alone, have you?