Jess Franco, I love his films (The Sadistic Baron von Klaus; Venus in Furs), and I hate his films (Lust for Frankenstein; Female Vampire). Sometimes I love and hate them at the same time (Oasis of the Zombies). One of his best films is The Awful Dr. Orloff, a film that I re-watched just a couple days before viewing Vengeance of Dr. Mabuse. The latter film suffers badly in comparison.
Vengeance of Dr. Mabuse borrows a great deal from the first Orloff film. Mabuse (Jack Taylor) has both a female assistant and a hulking Frankenstein monster henchmen in the Morpho vein. Said monster ends up turning against its master because of love (or lust) for a woman. The climactic showdown between cop and monster in both Mabuse and the first Orloff film are strikingly similar. If that was not enough, both films rely on bums out fishing to provide the police with a clue to the villains' hideout. Oh, and of course, both films deal with the abduction of a stripper. Although, strangely, in the print that I saw, Mabuse had less nudity than The Awful Dr. Orloff.
I know that some Franco fans like the way his films intersect, but, to me, The Vengeance of Dr. Mabuse shows a lazy director dropping in plot points from a movie he made better a decade before.
Finally, in all of the other Dr. Mabuse films, the man is a master criminal. He does not work for others! Yet, this Mabuse alludes to the trouble he and his cohorts will be in from "the organization" if they abandon the project. Mabuse as a mafia stooge. . . what a let down!