Premanand Maharaj Ji
How do I let go of hatred towards someone?
Pray, stay humble, and don't return hatred
Pray inwardly for strength, stay humble, and do not answer hatred or hostility with the same. The lesson is that Bhagwan takes care of the other person, and your heart stays cool.
Pray from within and the hatred will end. If you want the play of hatred to end, you must stay humble from your side.