Many people are cruel and wicked to others and yet they love to be shown mercy!

An armed robber who goes to a house, rape all the women in the house, kill the head of the house and steal away millions, appears before a court and pleads for mercy. Was he merciful to those poor innocent household?

A man, very rich with all the goods of life oppresses the poor man who is in need of food to eat; the rich man call his dogs to chase the hungry man who only came to beg for a few morsel of food to eat.[http://www.ackcity.net/show-mercy-to-others]

Don't ever show mercy to evil-doers!
Punish them mercilessly!
Who says 'vengeance' is of the 'lord'?
Not in my neck of the woods!

Dearly beloved, avenge not yourselves, but rather give place unto wrath: for it is written, Vengeance is mine; I will repay, saith the Lord.Romans 12:19

For we know him that hath said, Vengeance belongeth unto me, I will recompense, saith the Lord. And again, The Lord shall judge his people.
Hebrews 10:30