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Finding similarities in the characters :
Luke => Goku
Han Solo => Vegeta
Darth Vador => Frieza ou Majin buu ?
Bobba Fett => Cell (colors haha)

Your pick ?

Considering the role of a character, would not Darth Vader be a ginyu?

Well, if Vader is the father of Goku, that would mean Baddack in reality... Baddack used to work for Frieza, so Frieza would be the closet, no ? Why Ginyu btw ?

That's right.
It is very reasonable.