De acordo com "A História Secreta de Star Wars", de Michael Kaminski:
As mentioned earlier, Lucas was no stranger to comic books and not only was he an avid collector, but he bought reams of them looking for inspiration while writing Star Wars, and was even the co-owner of a comic book store in New York City. Jack Kirby was one of the most influential comic book artists in the history of the medium and was regarded as a legend by the 1970s, when he was as prolific as ever. It is here, in 1970, that he began his most epic creation, loved by serious collectors but largely ignored by mainstream audiences: his Fourth World serial, an epic of interconnected science fiction tales which formed a growing narrative and ran from 1970 to 1973, the year Lucas began writing Star Wars. The series would serve not only as an immediate influence on Star Wars, but perhaps a later influence, either consciously or residually, on the future shape of the saga in its sequels. For example, in The New Gods saga, a number of obvious influences immediately jump out. For instance, the villain of the series is named Darkseid (“dark side”). The hero (Orion) battles Darkseid, armed with a power which flows throughout the universe and is known as The Source (in other words, The Force) only to discover that Darkseid is in fact his own father.
As for visual inspiration, Darkseid was a hulking, caped, armoured character, adorned in black, with large boots, gauntlets and a helmet-like head.
The second Jack Kirby creation is Doctor Doom, one of the most memorable villains from the popular Fantastic Four series. Once a brilliant scientist and friends with the leader of the Fantastic Four, he became bitter with jealousy and was horribly scarred in a laboratory accident. He emerged as Doctor Doom, sworn enemy of the Fantastic Four and forever encased in a large iron suit, complete with a fluttering cape. Not only is his visual design very similar to Darth Vader’s but the character’s backstory is as well; it may be argued that this is coincidental, as masked characters in literature are often encased in their coverings to hide deformities, reaching back to 1909’s Phantom of the Opera by Gaston Leroux, but being such an important villain in the comic book world Doctor Doom’s influence may very well have been a conscious one. Supposedly Lucas himself has admitted the influence, though I am ignorant to such a reference. Doctor Doom first appeared in 1962, though the character would not gain prominence until the mid ‘70s.
It may be surmised in counter-point that these three characters were not necessarily deliberately copied by Lucas, but rather were swirling around in his subconsciousness as he prodded McQuarrie into the final Vader design, a mental catalog of villains and images that he had absorbed in his thirty years of viewing such material. On the other hand, the fact that Lucas provided McQuarrie with comic books (and showed a very hip awareness to the contemporary comic book scene at the time) and 1930s pulp pages for design references may demonstrate that these similarities are very much intentional.