Your radar for “something is wrong but I can’t put my finger on it” feeling. Intuition.
Edit: I’m noticing a lot of answers don’t cover covert things like:
Minor (constant) insults to undermine you and make you insecure,
Poking fun at things you find important,
Doesn’t own up to mistakes,
Continually refers to your mental state (depression, BPD, OCD, PTSD whatever it is) to gaslight you into thinking your reactions are not correct.
If they mess with your energy and you feel off kilter with them.
If they mimic your personality (when you know they’re not actually like this),
Actions don’t add up with words spoken.
When they need to convince you they’re a good guy.
Last, when you get butterflies or an anxious feeling with them. Good company doesn’t make you anxious, nervous, scared, or dissociative.
Edit: I’m noticing a lot of answers don’t cover covert things like:
Minor (constant) insults to undermine you and make you insecure,
Poking fun at things you find important,
Doesn’t own up to mistakes,
Continually refers to your mental state (depression, BPD, OCD, PTSD whatever it is) to gaslight you into thinking your reactions are not correct.
If they mess with your energy and you feel off kilter with them.
If they mimic your personality (when you know they’re not actually like this),
Actions don’t add up with words spoken.
When they need to convince you they’re a good guy.
Last, when you get butterflies or an anxious feeling with them. Good company doesn’t make you anxious, nervous, scared, or dissociative.