Adam-II was created by Phineas Horton in hopes of improving upon his earlier synthetic android the Human Torch. Shortly after being activated, Adam-II came to the conclusion that due to his nature as an android he was superior to humans and was quick to attack and imprison his creator. Adam-II began creating android duplicates of human beings, including Horton, with the intention of infiltrating the U.S. government and slowly conquering all of humanity.
Adam-II was created by Roy Thomas and Frank Robbins and first appeared in (the canon) What If? #4.
Adam-II is a would-be-world conqueror with a personality and motive similar to that of the Avengers enemy Ultron. Adam-II upgraded himself and renamed himself Adam-III in Captain America and Bucky #626.
Major Story Arcs
In the aftermath of World War II, the government appointed the Spirit of '76 to become a replacement Captain America and lead the Invaders (who redubbed themselves The All-Winners Squad) and the Human Torch soon learnt of Adam-II's existence and scheme for dominance upon discovering the android duplicate of their shared creator.
Human Torch and Toro were defeated by Adam-II but saved by the crimefighter Patriot who joined with the Squad to help stop Adam-II's plan to kidnap John F. Kennedy and replace him with an android duplicate. As the team searched for the evil android, the new Captain America encountered Adam-II. Engaging in combat, the hero was crushed to death by Adam-II and the entire conflict was seen by Patriot.
Taking the Captain America costume for himself, Patriot took up the mantle of the Sentinel of Liberty to lead the All-Winners Squad into battle against Adam-II, who attempted to escape but was apparently destroyed in an explosion.
Adam-II actually survived and began creating more and more android duplicates, including several androids modelled after Captain America. He also created an android who believed itself to be the son of the second Captain America which began to rebel against him leading to Captain America, Human Torch and the second Bucky fighting against a new and upgraded "Adam-III" who sough to conquer the world by inhabiting one of his android duplicates of Captain America.
A world where Adam-II had conquered the world and android life was dominant. Captain America and his three subsequent replacements found themselves in this reality and fought against Adam-II's rule. Patriot again defeated Adam-II and revealed he was responsible for the four Captains America being transported to this reality as he was dying of cancer and wished to have one last adventure.