Darth Vader was a Sith Lord, although I don’t remember him passing an entrance exam in Revenge of the Sith just lopped off Count Dooku’s head.
When Yoda died Luke became the last Jedi. Considering Luke’s meant to be the bright hope of the Jedi, he’s not doing a great job IMHO allowing the dark side arise whilst he grows a beard and no doubt bakes artisan bread on Craggy Island.
However Rey may become the Last Jedi, or Luke and Rey are the Last Jedi, all will possibly be revealed, or not as episode IX will follow. Knowing how the trailers for Rogue One meant his line probably got mangled and missed the last bit off ‘Jedi end… up being picked last for nerf herding’…