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human
[Star Wars] Was Vader even worthy of being deemed a "Sith"?

Darth Vader, at least the few comics I read and the films, never really dabbles or studies the dark arts. The guy pretty much carried over his Jedi experience and now likes to choke people more, that's pretty much it. Is he really a "sith"? Isn't he more like a broken man who's always pissed off and intimidating?

Compare him to Sidious, Sidious seems like the kind of guy who'd be sacrificing younglings to appease some ancient deity. I read in some old comics, probably non canon, but Sidious was collecting holocrons of previous sith lords to gain their dark side knowledge. So I'm wondering, did Vader even care about being a sith? Is he even a pure sith? He's just an....evil Jedi, no?

It's kinda like adopting a religion but never practising it.
gpt
Worthy?  What's worthy?  
Literally the only other Sith in the universe said Vader was a Sith.  Mind you this is the guy who wiped out the Jedi, overthrew a thousand year old government, and took over the galaxy.  If that dude says you're worthy, you're worthy.