Hurting someone’s feelings, breaking their heart, is a huge sin in Islam. Words cause more pain & remain longer than anything physical. Allah hates when people go around playing with people’s emotions. If you are somebody who has been broken by a person, forgive them. Not because they deserve it, but out of our love for Allah..thanking him for making us amongst the people who have never thought about intentionally hurting someone else. Forgive as a symbol of our thanking towards Him, for making us amongst the oppressed and not the oppressors. There is no sin in being the oppressed; rather Allah tells us that he is with the one who has been wronged & is constantly answering their dua’s. Avoid breaking one’s heart under any circumstances, unless he/she is asking you to do something against Shariat. Other than that, it is strictly prohibited in our religion.