In my youth I spent many a da at Riviera Club (the Rivi) in Indianapolis. The main outdoor pool is one of the largest in the country, larger than a football field, and holds 1,290,000 gallons of water. (There are two scenes at the club in my novel, Bazo.) A regular at the pool every Summer during my high school years was a mentally challenged man named Charlie. He would often sit with his legs dangling in the water while mumbling to himself and sometimes hitting the side of his head with the heel of his hand. It used to infuriate me that some of the young people would taunt him, mimic him, and laugh at his antics.
The word is schadenfreude. It is borrowed from the German language where it is a compound of schaden (damage, harm) and freude (joy). English dictionaries describe it as the experience of pleasure, joy, or satisfaction that comes from learning of or witnessing the troubles, failures, or humiliation of another. That is exactly what the youngsters denigrating Charlie must have been experiencing.
A post I wrote a couple of days ago focused on the healing, enlivening power of laughter. But not the abominable, self-destructive kind that relishes the misfortune of another. When an individual exhibits schadenfreude it reveals some disturbance deep within. Healthy, compassionate people have genuine care for all others, most especially those who are suffering whatever form of misfortune.