I’m fortunate to have been happily married for awhile but some of mine would be -
Being into gaming. I could not deal with being with a man heavily into it. Hard line for me and would be the biggest turn off.
Overbearing mothers. Being useless around the house/in the kitchen is usually a sign of a mollycoddled son. Avoid.
Game playing in the relationship - deliberately holding off on replying to messages, playing hard to get, etc.
Having a female ‘best friend’... usually a recipe for disaster too.