Mercy is one thing, but can you find it in yourself to actively love someone who hates you or wants to hurt you?
Jesus was clear about this. He has given us a command to love our enemies.
The Spirit gives God's people the strength to love when love seems impossible. It even seems as though God deliberately uses such foolishness to save sinners.
You can read accounts of those who loved their enemies while being killed for Christ in Fox's Book of Martyrs.