Dr. Black, Mr. Hyde gives us Bernie Casey (Under Siege, Revenge of the Nerds) as Dr. Henry Pride, a devoted scientist who researches experimental liver transplant techniques and volunteers at an inner-city clinic during his free time. He seems to be living the perfect life, but as one of his patient tells him via clumsy exposition, he almost seems to be more white man than black man (In the same scene, he tells a female patient, 'Your hepatitis is almost gone!' making it clear to the audience what occupation this patient works in).
While experimenting, Dr. Pride finds a serum that turns normal brown rats into hyper-vicious white rats, and then (of course) proceeds to take the serum himself, transforming into a powdered, made-up version of himself that every other character in the movie insists looks like a white man.
In reality he looks more like one of the zombies from The Omega Man, but who really cares? The movie proceeds to follow the standard Jekyll-and-Hyde formula as Dr. Pride lives his double life - upright and noble by day, frequenting the bars and prostitutes of South Central Los Angeles by night. Finally, it all ends with a King Kong-esque finale at the Watts Towers (literally - Casey climbs up them until he's shot down). It's not much of a movie, padded out with overlong scenes of Casey transforming and grimacing and moaning and so on, but it's at least passably entertaining for those who've seen Blacula and were left hungry for more.
Next was Black Fist, also known as Black Streetfighter. The biggest thing that I got out of this movie was the bizarre notion that, in the mid-70s, promoters could get huge multi-ethnic audiences of all ages to show up in junkyards to watch bare-knuckle street fights, no holds barred, in which at any moment a competitor might get tossed directly into you. The presence of so many middle-aged ladies and white couples in these scenes was highly amusing to me.
Otherwise, it's your standard action-revenge-template movie, in which Leroy Fisk involves himself in the corrupt street-fighting world and can only escape through extreme violence. Dabney Coleman shows up as a corrupt cop and steals just about every scene that he's in until being frozen in a meat-locker. Philip Michael Hall, of Miami Vice fame, is also in this movie playing two different characters, a loveable crackhead and a hapless informant.
Overall it's a much sloppier movie than Dr. Black, Mr. Hyde, but it's also less padded out, which means that we get a higher degree of hysteria and bloodlust. My two favorite moments of it come here - zoom forward to 4:10 for a scene of amazing overacting between Hall and the junkie girlfriend of a mob boss; and for this dialogue tidbit between a henchman and a crimelord (here at 4:00, but unfortunately split in two on Youtube):
"Mr. Ingo? Logan will not bother you any more. I wasted him for you. And I did it in a very sophisticated manner. I tricked him! I wined him, I dined him. I took him to a disco, we were having a lot of fun! Then I killed him."
Neither of these movies is good, per se, but both are amusing enough to be watchable, and Black Fist is marginally better by virtue of having more energy and narrative surprises.
Dr. Black, Mr. Hyde: 3/10
Black Fist: 4/10