For example, when Miriam and Aaron talked against Moses. The Lord got angry with them and struck Miriam with leprosy. And He is the example we are to follow. How He dealt with the woman caught in adultery. If you remember the definition of kindness, it is giving a blessing that is not deserved and withholding punishment deserved.
Nobody likes to be taken advantage of.
If you feel you have been mistreated and your kindness has been taken advantage of, then the Lord has a word for you, today. Beloved, God does not miss anything. We must also realize that hurting people, hurt people. It's such a simple kindness. Hold a door open for someone.