I'll give you a concrete example...
At the age of 11, I moved to another city and I had to change college for my 5th grade. I didn't know anyone, no student, and very quickly I attracted all kinds of teasing and in particular from a boy, whom I'll call Luc, who had given me an unpleasant nickname. The first weeks after the start of the school year were difficult and Luc's incessant harassment disturbed me. It turns out that at that time I had difficulty in English and my parents had bought me the audio cassettes as an option with the textbook. One day, the main teacher, in the middle of class, asked the whole class if anyone had these said tapes so that Luc could make copies. Nobody answered! I then turned to him and said: "I have them! I will bring them to you tomorrow". He was completely destabilized! The next day I brought him the tapes. I got a "thank you" and Luc never harassed me again.
This is how to kill someone with kindness 😉