if you love someone, hate can be one step away if you are disappointed, hurt, or thwarted.
going the other way? not so much, except in the movies.
Love and hate are just a thin line apart!
I don't know about how many steps it would be, but I believe it is very possible to love, especially if that is what you really want to do. I suppose the number of steps involved has to do with why you had such hatred for the person in the first place and whether you can find it in your heart to forgive. Also, if you can see that person as someone lovable- with an altered perception that looks for the good in contrast to seeing all the things that led you to hate in the first place.
Love can come from any where, but there is a reason you hated them right ? So what changed. Maybe you got to know him better or maybe he's kinder. Figure out what happened and then you can work things out. Since you love that person, you should make sure there are no hateful feeling still.
Love and hate are very close I'm my opinion.