Designated Hero: Just about all the leads are rather unsavory or unscrupulous to one degree or another.
Tuck, basically the main hero and T.J.'s former fiancé is a rather cutthroat businessman who wants to buy her out. He also makes several advances on her despite her continued protests, even locking them both in the same room (which some might consider harassment).
T.J. really didn't do anything morally objectionable, but is rather callous.
Bromley, the paleontologist is one of the more innocent of the bunch. But helps the fanatical group of gypsies steal T.J.'s horse in hope of following it to its home without a second thought of who the gypsies might hurt, or what the loss of the animal might do to T.J.'s show.
The Gypsies who take it upon themselves to free Gwangi from his cage in an effort to set him free. At least two are killed for their troubles, and Gwangi escapes, killing Bromley and possible dozens of innocent people in the process.
Unintentionally Unsympathetic: The protagonists. Gwangi was just an animal minding his business in the Forbidden Valley until some greedy foreign capitalists show up to kidnap him and drag him off to be exhibited in a circus show. And then burn him alive.