I think this question is assuming you're looking to date, not just for sex, so I'll answer it accordingly.
First off, being on Tinder is a red flag itself in my experience.
I've hooked up with 12 women from there, and at best a third of them were dating material.
So many of the women on there are just looking to hook up / rebound. I'm in my twenties, I'd imagine this trend decreases as you get older.
I have not seriously dated anyone from Tinder, despite being on there looking to date and having an abundance of options with over 1000 matches.
IRL social connections have worked much better in my experience.
Enough rambling, my red flags are:
-Excessively sexy / slutty vibe (they're not trying to date)
-No bio (they're just testing the waters, not trying to find someone. Or they're just boring)
-Political positions in bio. They're gonna be dumb.
-They sound like a workaholic. I prefer a successful woman, but career obsession can go too far.
-No interest in having kids
-Non-standard piercings (almost always associated with psychological issues in my experience)
-Weird niche interests that suggest they spend way too much time online
-Any mention of video games or anime. These women are just as lousy as male gamers / weebs
-Extremely puritan vibe. Probably won't relate much to a girl who barely drinks or has never smoked weed
-Height requirement, unless they're a real tall girl, in which case I get it
-Atheist
-Massive social media following, like upwards of 3k on Instagram. Likely to have issues with narcissism. Could make exceptions to this if they're doing something beyond posting thirst traps
-Giving off dark, female sociopath energy
-Goth vibes (gonna be nihilists)
-Legitimately bisexual, not bi in the trendy fake modern way. I have just had too much bad experience with this one, they tend to be indisposed towards monogamy
-Mention depression or ADHD in their bios. They're gonna be a piece of work. I have mental health issues myself but putting this in your bio just generally shows you don't have your act together at all
-Short hair, like shorter than neck length. (Huge negative signal on personality to me, I actually don't mind the look that much)
Green flags:
-Mention art or hobbies. Likely to be interesting, thoughtful person.
-They exercise, without making it their whole personality
-Like the outdoors
-Photos with friends, and the friends look like my sort of people
-They look generally happy
-Their bio is genuinely funny