What is it like when an INFJ "hates" someone?

Just as what the title states and maybe a few more add ons as well:

What do INFJs do when they hate someone? Is it possible to suddenly hate someone whom you used to love dearly? What should the other person do?

"Hate" might be a really strong word here as well. Other possible emotions could be anger or indifference. What is it like when an INFJ is feeling those emotions?