Well since I've become single again, it won't hurt for me to set my boundaries for any future encounters of the romantic kind, redundancy be damned.
Smokers. My primary turn off is somebody who regularly torments their own lungs and pollutes the air with shit like that. I don't care if it's vape, weed, or tobacco, my health is very sensitive and I will not willingly hang around people who have it as a hobby for extended periods of time. Living in the city is bad enough.
Vegans and Conservative Religious people. Now you'd think that they don't belong in the same category, but the reason for both is that I just won't share my life with someone who is in all likelihood practically guaranteed to push their lifestyle choices on me.
Unhygenic people. I personally don't consider myself to be the utmost paragon of hygiene and all things clean, but at least I put effort into keeping clean. I would expect at least something similar from the other.
STDs. Having one is a definite deal breaker. I want to enjoy my already short life as much as I can, you know?
Depression. I personally don't hold anything against people with depression in general, but it was the main deal-breaker in my last relationship as it just got me so emotionally burned out from attempting to understand the problem, handle it, and make sure they didn't kill themselves while trying to maintain the kind of emotional investment I had at the start. It's just not something I'm willing to go through again.
Nit-pickiness. Look, what I want is a life partner, not a substitute mother. I'm fine with criticism, but people who tend to nag on every little thing have a tendency to make others feel like they're below them.
Air-headed Materialistic Normies. People are most often born with this thing called a brain. I prefer engaging in a relationship with people who know how to actually use that part of themselves properly.
This probably isn't all of it, but it's fresh from the semi-salty post-breakup mentality I've gotten so it's as good as I've got.