Lt. Col. Glenn Manning is the primary antagonist of The Amazing Colossal Man and its sequel, War of the Colossal Beast - both rather infamous examples of the Giant Monster sub-genre of Science Fiction.
The Amazing Colossal Man
Lt. Col. Glenn Manning, an officer in the U.S. Army who suffers serious burns to over 90% of his body and hair loss following an inadvertent exposure to plutonium radiation from a bomb blast. He miraculously survives the explosion and his burns completely heal, but the radiation causes him to abnormally grow into a 60-foot-tall giant. At this size, his heart is unable to supply sufficient blood to his brain and he gradually goes insane.
Army doctors attempt to halt and reverse his growth with a formula, but after getting injected with the cure, he grabs the needle and spears one of the doctors with it, killing him on the spot. He then escapes from confinement, "kidnaps" his girlfriend, Carol Forrest (played by Cathy Downs), and wreaks havoc in Las Vegas before being cornered by the Army at the Boulder Dam. After releasing Carol he is shot and appears to fall to his death in the Colorado River.
War of the Colossal Beast
Upon hearing of several recent robberies of food delivery trucks in Mexico, Joyce Manning, Army officer Lt. Col. Glenn Manning's sister (though in The Amazing Colossal Man, his fiance said he had no surviving family), becomes convinced that her brother survived his fall from the Boulder Dam at the end of the first film. Along with Army officer Major Mark Baird and scientist Dr. Carmichael, she goes to Mexico to look for him.
It is discovered that Manning, now grown to 60 feet tall after being exposed to plutonium radiation, survived his fall from the Boulder Dam at the end of the previous movie, but he has gone insane and part of his face was left disfigured following his confrontation with the Army there, turning him into a zombie-like creature.
Not only has the plutonium radiation mutated him into a 60 foot disfigured freak, it also has conferred other benefits; drastically reducing his vocabulary and diet - he now appears capable only of uttering simple variations on "aarrrgh" (although he does manage a single strangled "Joyce!" at the movie's end) and only eating loaves of bread (by the truck load).
Manning is captured, drugged by the Army, taken back to America, but he again escapes and goes on a rampage through Los Angeles and Hollywood. Eventually, Joyce makes him snap to his senses and realizing what he has done, he kills himself by electrocution (somehow causing the movie to change from black and white to color for the final minute) on high-voltage power lines around the Griffith Observatory. The ending, involving electrocution, is almost exactly like the death of the 50-ft Woman.
