Is sue now only understood as an adversarial term? Since the US seems only to use it to mean a legal weapon against some person or entity, it's not heard as request or entreaty. Is this the case in all English-speaking places?

Outside of historical dramas I think I've only heard it used in the sense of suing someone in court.

So, a traitorous eytmology! From the Latin, "sequi," we get "suitor" and suit; one a follower, the other an opponent. But then if the suitor is of the romantic variety, it might devolve into the latter term eventually.

Interesting thought, Geoff. But I do agree with Bob that "sue" itself seems to only refer to court cases. Of course, there is always the lady's name, Sue!