What is the cruelest thing anyone has ever done?

During my school time there was a very bad boy. Always messing up with young ones. One day he brought a very young puppy. He was around one week old. He was ruthlessly throwing him from the bench and after sometime few more boys joined him. They started throwing the puppy from one to another. It was beyond my self control. I stood up and argued them to leave the puppy.
I don’t know what was his intention but he punched me and started to play with puppy again. I was very angry.
By physic I wasn’t challenging during those days but I don’t know from where I felt a flow of energy inside of me. I grabbed his collar and punched twice in his face. The puppy was free. I took him outside where his mummy was waiting for him.
They were happy :)
Did you fought for a good cause (not physically)