It's actually a common misconception that Darth Vader made C-3PO. In fact, C-3PO was created by Anakin Skywalker, who later became Darth Vader, but he did not have a direct hand in the droid's construction.
In Star Wars Episode I: The Phantom Menace, we see a young Anakin Skywalker working as a slave on the planet Tatooine. It is here that we meet a protocol droid named C-3PO that Anakin has been putting together.
However, it is important to note that Anakin's involvement in C-3PO's creation is limited to repairing and improving an existing droid, rather than building him from scratch.
Later on, in Star Wars Episode IV: A New Hope, C-3PO and R2-D2 end up on the Death Star, where they encounter Darth Vader briefly but not connection is made.
So, while Darth Vader did have a connection to C-3PO through his past interactions with the droid, he did not actually create him.
HOWEVER - this relationship is put to great use as a metaphor throughout the saga
Later on, in Star Wars Episode IV: A New Hope, C-3PO and R2-D2 end up on the Death Star, where they encounter Darth Vader briefly but not connection is made.
So, while Darth Vader did have a connection to C-3PO through his past interactions with the droid, he did not actually create him.
HOWEVER - this relationship is put to great use as a metaphor throughout the saga
