Is it possible to spot most red flags before entering a relationship?

So many people end up getting hurt, emotionally, by getting involved with people who are controlling, unfaithful, liars, or physically or verbally abusive.

Do you think it’s usually obvious that these jerks are showing signs of their bad behaviors before they get involved with other people? Is it possible that most jerks are able to control or hide their bad behavior until after they’ve gotten involved with someone? Or do you think that some people are just too sucked into relationships, whether it’s by love, or lust, or loneliness, that they simply can’t see the signs, or choose to ignore the signs, until they’re already involved with or married to the person?