1John 3:15 - Whosoever hateth his brother is a murderer: and ye know that no murderer hath eternal life abiding in him.

I know some people who harbor hate and unforgiveness toward others. That is a scary way to be. If I am interpreting this verse correctly, it seems to be saying that those people are not Christians and have no hope of Heaven. If you feel hatred toward others, search your heart and make sure of your relationship with God.