This is the 17735th most frequent Polish word.
znęca
"Znęca" means "he/she/it abuses" or "torments" in English.
In this sentence, 'znęca' means 'is mistreating' and describes the act of causing harm or being cruel to someone.
On się znęca nad słabszym kolegą.
He is mistreating his weaker friend.
Here, 'znęcać' is used in the infinitive form to express a general prohibition against causing harm or being cruel.
Nie wolno się znęcać nad zwierzętami.
One should not be cruel to animals.
In this usage, 'znęca' describes mental self-cruelty or the act of being harsh on oneself mentally.