Violence or aggression towards animals or pets.

When they talk about somebody else behind their backs.

I'm a misanthrope, I don't have any respect for anyone to begin with.

No rational thinking.

Believing in pseudoscience or spiritualistic flim flam (astrology, crystals, energy) and being anti-science.

There's a lot more but that's good enough.

If they are, in a completely literal sense, impossible to predict.

I have reached a point of no return (no return of respect) with a high ranking person recently who started out as friends with me. I had a lot of controversy surrounding me, but she promised she knew none of the hearsay was true. Then she cut me out, and it took me a moment to learn why. Then some months later she reached a point where she restarted her feelings for people and eliminated her grudges. We were friends for a while, and all seemed fine, but then same exact thing happened, she promised nothing was going to happen before she cut me out again. Again, it took me a while to learn why. I would leave that general area, but we would find each other elsewhere one day, and she seemed fine with me. All seemed well. Then I went to ask her a question and discovered she cut me out again. At this point, another friend of mine got involved, not giving her a good time (I tried stopping him, but every time I did, it would still be deemed my fault that was happening), and then she declared a truce and asked if I would accept. I consented on the condition everyone knew about the truce and that it wasn't just a privately negotiated thing. She accepted, and I have proof of the truce, and to celebrate the truce, I was introduced to her inner circle. However, I was removed from her inner circle twice, once quickly the first time and once after asking to come back in a few months later, with another few months where I wasn't removed. She then came to me and said "sorry, I removed you because I have people in my group who don't like you, no hard feelings" and I was basically like "alright, I understand". Half a month later I went to ask another question only to learn I was ghosted again. And this, combined with another person coming to me saying they bore proof she was talking about me behind my back (the prime condition of the "truce" was to not do that), I had had it. I ended the truce and lost any respect for them, and I'm not afraid to show it.

I've actually had many, many, many encounters similar to this, and so have some people I know; once in a while people who become on good terms with me again cite things like "mental illness" and "shutting [person's self] down trying to cope from being overwhelmed". I don't care if you have a delusion disorder, if you're going to see other human beings as so insignificant in your seemingly solipsist mind as to think people with different ways of perceiving a situation can understand a part of your experience they don't necessarily have any reason to think exists, that is simply reckless and you're just a jerk. Many of these people also often say "well if you would just read the room you would know what the reasoning is" but unspoken words spell out differently for everyone because it's like looking at a mirage in the distance. The "writing on the wall" is a myth, in the end it refers to jibberish because at least language is communicated.

If they believe in ghosts

a lack of awareness of current events in the world around them

Demanding it.

Respect is earned, not automatic.

Taking advantage of kind people. By all means you don't need to turn down kindness, even if you're joking to make light of your need to ask for kindness that's fine but if you take their kindness as expectation, it really hurts. My mother was always willing to help those in need and people would always use her like it was their right until she broke down. I'm currently trying to convince my senior to include me in more of his meetings because he seems to be in a similar position and I'm ready to help him say no