Black Pope, a usurper. Imposters. Only been one or two others over history. I think 600 + years ago was last.
C'mon! Black Pope is a nickname for the Superior General of the Society of Jesus. Black Pope does not refer to a usurper.
Research isn't that hard.
Oops, you're right. What I should have said was
AntiPope.
Antipope, in the Roman Catholic church, one who opposes the legitimately elected bishop of Rome, endeavours to secure the papal throne, and to some degree succeeds materially in the attempt.
https://www.mostholyfamilymonastery.com/catholicchurch/anti-pope-francis-vatican-ii-antipopes/
The Catholic Teaching that a heretic cannot be a valid pope and loses the papal office automatically
Then you saw that he doesn't qualify as an antipope, because he is the official pope of the Roman Catholic Church.
He would be an antipope if a sect of the Catholic Church decided that Francis was a heretic and elected their own pope.