Any object or situation that is intensely disliked as a whole.
There is a subtle difference between using "hated" in this way, and in the traditional use "it is hated (by many)". In this case, "Hated" is used like the word "Hateful".
It's often used by itself, or as a one-word reply.
"I saw a cockroach run up the wall! Hated."
"I got pulled over today...."
"Ahhh.. Cops. Hated." (The person is sympathizing with the one who got pulled over by saying how much he hates cops too.)