Could Macbeth kill Macbeth?
To specify, and partly because I assume you've dealt with the most basic version of that question, here's some specific permutations of that question.
Could time-traveling future Macbeth kill his old version or vice versa?
Could a clone of Macbeth who's realized she's trans kill Macbeth?
Could Macbeth kill himself after his parents realize they're both non-binary?
Could the historical figure Macbeth kill his fictional counterpart or vice versa?
(cracks my knuckles and leans forward in my chair)
Macbeth from the Future: No. Both are man of woman born and both have the prophecy. Neither would be able to kill the other.
Trans Woman Clone of Macbeth: Yes. GC and UBC. Potentially BPC as well depending on who made the clone. If the prophecy applies to her, Macbeth would not be able to retaliate.
Suicide w/ NB Parents: Yes. Macbeth himself would then apply for BPC.
Historical Macbeth: No. H!Macbeth is a man of woman born (presumably; not much is known about the real person). H!Macbeth also does not have the prophecy, meaning F!Macbeth could retaliate and kill him.
Some more you didn't specifically ask about but would probably get brought up otherwise:
Suicide: No. Macbeth is a man of woman born. Also, Shakespeare would 100% do a scene where Macbeth has reached a breaking point and tries to end it all but finds that he physically can't.
Copy of the Script and Stage Directions for the Play Macbeth: Yes. An inanimate object and therefore genderless, also the play was originally written (not born) by William Shakespeare, a man. GC, UBC, BPC. That is, unless it is being used as a murder weapon, in which case we would analyze who set it into motion instead of the script itself.
Alternate Universe Macbeth: As long as this Macbeth is still a man of woman born, then no. Also, as long as the prophecy isn't different between the two, neither would be able to kill the other.
Specifically from a Universe where everything is the same except "No Man of Woman Born" is a name and "Macbeth" is a term meaning anybody but a man of woman born: Yes. NoManofWomanBorn would count as a Unique Exception for Macbeth, while Macbeth would also count as a Unique Exception for NoManofWomanBorn, meaning they would be able to kill each other despite both of them being man of woman born.
Suicide after legally changing his name to No Man of Woman Born: Yes. He would then be a Unique Exception for himself.
If there's anything else obvious I missed you can let me know with the specific scenario you have in mind via either the ask box (it'll take a while for me to get to it) or putting it in a reblog of this post (it'll probably be way faster this way).
Thank you for your submission!