There's a super thin line between love and hate, I know that's a cliché, but its true.

Besides, IMO the opposite of love isn't hate, its indifference.

I can only hate someone I truely love/d, indifference means a complete absence of love because you couldn't care less anyway.

Idk what to do in your case though, but if you want to remain estranged from this person, then I don't suggest focussing on hate.
I suggest letting go, moving forward and reaching a point of indifference.