Psychiatrist Dr. Leonard Samson came to General T.E. "Thunderbolt" Ross with a plan to cure Ross's daughter Betty, who had been transformed into a crystalline form through a blood transfusion with the Sandman. Samson had technicians devise a cathexis ray projector that would drain off gamma particle energy and psionic energy from Bruce Banner as he transformed into the monstrous Hulk whom General Ross had long hunted. Samson theorized that as a result of this process, Banner would be cured of the physiological instability that continually transformed him into the Hulk. Hoping to save Betty and to be cured himself. Banner willingly participated in the experiment. The cathexis ray succeeded in turning Betty Ross back to normal, employing Banner's psionic energy.
However, most of the psionic energy drained from Banner as well as a considerable amount of his excess gamma radiation remained within the cathexis ray projector. Motivated by scientific curiosity, and probably by a desire to gain superhuman powers for himself, Samson irradiated himself with the energies remaining within the projector. The result was that the slight, brown-haired psychiatrist was transformed into a massively muscled, green-haired superhuman with gamma-boosted strength. Banner himself seemed permanently cured, but he broke emotionally under the strain of seeing Betty, the woman he loved, being romanced by Samson and exposed himself to gamma radiation, thereby undoing the cure.
Samson later lost his superhuman physique and power when he took a blast of concentrated gamma radiation intended for the Hulk. However, months later Samson regained his gamma-mutated form and superhuman strength when he was bombarded by intensive radiation from an exploding gammatron, an experimental gamma-ray generator. He has remained in this form ever since. Doc Samson, as he has been nicknamed, has long sought to capture and permanently cure the Hulk. Samson worked as a university teacher during the recent time that the Hulk was traveling through different dimension, unable to return to Earth, but Samson returned to his pursuit of the Hulk once the monster reappeared on Earth.
Civil War and World War Hulk
During the Superhero Civil War Samson joined the Registered heroes and fought against the Secret Avengers. Recently, the Hulk returned to seek revenge on the Illuminati, who exiled him to space. Doc Samson helped evacuate the people of New York. Then he battled the Hulk and the Warbound. He was defeated by the Warbound and imprisoned.
Following the Skrull invasion, Doc Samson led a support group meeting with those that had been replaced by Skrulls. Later, on Air Force One, he attempted to disclose the full activities of Norman Osborn within Thunderbolts Mountain to the new United States President. Before Samson was able to play the evidence, Osborn's new Thunderbolts hijacked the plane: the Ghost took the evidence, Eric O'Grady implanted a gamma-emitter on the back of Samson's neck causing him to grow angry and more powerful in a Hulk-like manner, and someone wearing the Green Goblin's costume attacked the airplane. Samson's increased anger caused him to attack the President, but he was phased out of the plane by the Ghost. Osborn reasoned that, in his enhanced state, Doc Samson probably survived the fall, and released a global warrant for his arrest, suggesting that Samson attempted to kill the President.
A new Red Hulk appeared, and revealed that Bruce was no longer comatose, and was being imprisoned by the US military. However, the Helicarrier crashed near New Jersey. Tony Stark ordered Maria Hill to investigate and search for survivors. Clay Quartermain's corpse was found mangled and ravaged, and the area bathed with gamma radiation. General Ross and Samson's bodies were missing. Leonard's coat was found ripped and shredded in a Hulk-like fashion, exhibiting higher Gamma Radiation values than every other item in the wreckage.
M.O.D.O.K. placed Samson under mind control producing a split personality. This led to a powerless Leonard who was defined as the good one and an evil Samson whose abilities are greater than She-Hulk's. Samson shot Rick Jones and dragged him away after he attempted to reveal who the Red Hulk really was. He then engaged She-Hulk in combat but it was cut short by M.O.D.O.K. who fired a laser, knocking both unconscious and reverting Samson to Leonard. A battle between Red Hulk and Hulk caused an explosion. After the Red Hulk depowered the true Hulk, Samson double crossed Red Hulk to punish him for his disobedience. Afterward, Sampson's darker persona took control once again, under M.O.D.O.K.'s surveillance.
Reverted, Doc Samson was killed attempting to help a returned Hulk contain all of the Gamma radiation from the Hulked-Out Heroes.
Recently, Doc Samson was among the many deceased resurrected during the Chaos War, along with Glenn Talbot, Hiroim, Jarella, Rebecca Banner, the Abomination, and Brian Banner, who had the ability to transform into a replica of the Devil Hulk at will.