Full disclaimer: I don’t date so I am talking about in friendships in general.

Being over-apologetic. And by that I mean they are quick to apologize any potential conflict.

Apologizing is a good thing, however if they consistently go out of their way to apologize without you even mentioning anything was wrong, chances are there are more dark/nefarious plays at hand such as manipulation.

I have missed that flag a few times in friendships and they ended up turning toxic over time. Some were recoverable, some wern’t