I guess first we have to reflect and figure out why am I hating this person? Why are these emotions being evoked in me? Why am I attaching myself to these negative emotions? The feelings we have towards others, can teach us a lot about ourselves too.
And then perhaps try and recognize that we are all divine. That this person we hate, the divine also lives within them. So should we hate them? We definitely will not like everyone, and that is OK. We just have to be able to not attach to the hate. Let it go, focus on our own lives, and developing the best in ourselves.
I don't know it hate is a sin per se, however, in Sikhi we are encouraged to remain in chardi kala, and to uphold compassion.