In every Kamen Rider franchise, there are a set of villains that we either love of hate, but most of the time, love. Unbeknownst to us, before they became villains, they have their own past as humans and the said past was written on official sources and if lucky enough, the Japanese Wikipedia. Here are some of those stories found by the anons of /m/ regarding the past of Shocker and Gel-Shocker's famed villains.
Doctor Shinigami is a half-Russian, half-Japanese named, Ivan Tawanobicchi (イワン・タワノビッチ). He gained the nickname, "shinigami" while he was still a child because many people died shortly after meeting him even if he is not actually involved with their deaths. He earned the title "doctor/hakase" after he graduated and became a famous researcher.
Shinigami was with the Nazis during WWII and working on a way to make replacement bodies for dying people. He even tested this out on his father, which was a failure. The reason? His sister got sick and her body was frozen after an accident in the artic. After the end of the war, the good doctor travels the world following rumors of a monk who can revive the dead.
After many years of searching, Shinigami finds the monk called Chan Mao in Tibet and begs him to tell him his secret. Mao rejects this man as his student because he is too bound to human emotions; the love he has for his sister. Few years later, Chan Mao somehow turns up in South America and Shinigami tracks him down... only to find that Mao is dead.
But Mao isn't really dead. Shinigami found his body, but it turns out that Mao managed to transcend his earthly body. Mao can now create a physical form at will, he can also overtake the bodies of others to use. By this time Mao wants to take over the world to unite it as one being and says he'll help Shinigami find a way to save his sister if he joins him. After losing his body, Mao also began to go by a new name, Great Leader. It's also hinted at that all the Shocker grunts are just creations of Mao, not really alive.
He works in modified human research for Shocker, but his experiments are defeated by Rider 1 in Europe (their European battle is actually briefly shown in the series). Hongo's constant interference in Shocker's operations make Shinigami focus on defeating the Rider (presumably, this is why his sister isn't referenced in the show).
He moves to Japan to fight Rider 2. After he leaves Japan again, he goes to Brazil and fights against Rider 2 there. However, yet again, he was unable to defeat the Rider. He finally went through a reconstruction process himself, becoming Ikadevil. Shinigami predicted that he soon would die in battle and so returned to Japan to have a final battle against Hongo.
Born Bakarashin Iinodebitchi Zol (バカラシン・イイノデビッチ・ゾル), Colonel Zol was a former Nazi member born in Leipzig, Germany. Worked for a while in a concentration camp near Birukenau, and lost his eye due to a gas leak there.
He was invited by the Great Leader to join Shocker after the second World War had ended. He was considered a war criminal, but still was proud of his military past, keeping his uniform to show his pride.
He altered his own body using a process that turned him into a werewolf. Moved by hate, he brought a wave of destruction to the Middle East, aiming to build Shocker's utopia there. Afterwards, he was called by the Great Leader to the Japanese branch.
As an addition, General Monster was an officer under his command during the war. He joined Shocker but was killed and his body frozen to be preserved. Afterwards, he was found and restored by Neo-Shocker, joining them as a high ranking commander.
And Ambassador Hell's backstory is basically the one from Spirits. That's all canon for the tv show too, aside from him being actually the second choice for the position in Shocker.
Lastly, Gel-Shocker's General Black, he was once an Army official of the former Imperial Russia. He got to the position of General while still young due to his cruel and effective tactics.
His cruel methods of torture and boldness in combat spread fear to both his opponents and the farmers of his own country. After the fall of the empire, he was approached by an esoteric Buddhist group called "Geldam". Involved with the new group, he traveled to Africa, where he continued a perfect terror campaign. He kept his old uniform and ranking from the Russian Empire.
Finally, he was contacted by Shocker's Great Leader and went to Japan, founding "Gel-Shocker" there. The medals on his chest were presented by Nicolai II himself, the Russian army and even Gel-Shocker's Great Leader.
The extensive Doctor Shinigami backstory (which includes him being part of the Nazi, his love for her sister) was found on the book written by show producer, Tooru Hirayama entitled, "My Beloved Characters" while the rest of the entries was found Japanese Wikipedia.
Also, the same /m/ thread has a back story about Kamen Rider Amazon's Garanda Empire but since most of the stories that I found are related to Shocker and Gel-Shocker, I decided not to place it. You can check it out in the link found on top of this post.
Doctor Shinigami is a half-Russian, half-Japanese named, Ivan Tawanobicchi (イワン・タワノビッチ). He gained the nickname, "shinigami" while he was still a child because many people died shortly after meeting him even if he is not actually involved with their deaths. He earned the title "doctor/hakase" after he graduated and became a famous researcher.
Shinigami was with the Nazis during WWII and working on a way to make replacement bodies for dying people. He even tested this out on his father, which was a failure. The reason? His sister got sick and her body was frozen after an accident in the artic. After the end of the war, the good doctor travels the world following rumors of a monk who can revive the dead.
After many years of searching, Shinigami finds the monk called Chan Mao in Tibet and begs him to tell him his secret. Mao rejects this man as his student because he is too bound to human emotions; the love he has for his sister. Few years later, Chan Mao somehow turns up in South America and Shinigami tracks him down... only to find that Mao is dead.
But Mao isn't really dead. Shinigami found his body, but it turns out that Mao managed to transcend his earthly body. Mao can now create a physical form at will, he can also overtake the bodies of others to use. By this time Mao wants to take over the world to unite it as one being and says he'll help Shinigami find a way to save his sister if he joins him. After losing his body, Mao also began to go by a new name, Great Leader. It's also hinted at that all the Shocker grunts are just creations of Mao, not really alive.
He works in modified human research for Shocker, but his experiments are defeated by Rider 1 in Europe (their European battle is actually briefly shown in the series). Hongo's constant interference in Shocker's operations make Shinigami focus on defeating the Rider (presumably, this is why his sister isn't referenced in the show).
He moves to Japan to fight Rider 2. After he leaves Japan again, he goes to Brazil and fights against Rider 2 there. However, yet again, he was unable to defeat the Rider. He finally went through a reconstruction process himself, becoming Ikadevil. Shinigami predicted that he soon would die in battle and so returned to Japan to have a final battle against Hongo.
Born Bakarashin Iinodebitchi Zol (バカラシン・イイノデビッチ・ゾル), Colonel Zol was a former Nazi member born in Leipzig, Germany. Worked for a while in a concentration camp near Birukenau, and lost his eye due to a gas leak there.
He was invited by the Great Leader to join Shocker after the second World War had ended. He was considered a war criminal, but still was proud of his military past, keeping his uniform to show his pride.
He altered his own body using a process that turned him into a werewolf. Moved by hate, he brought a wave of destruction to the Middle East, aiming to build Shocker's utopia there. Afterwards, he was called by the Great Leader to the Japanese branch.
As an addition, General Monster was an officer under his command during the war. He joined Shocker but was killed and his body frozen to be preserved. Afterwards, he was found and restored by Neo-Shocker, joining them as a high ranking commander.
And Ambassador Hell's backstory is basically the one from Spirits. That's all canon for the tv show too, aside from him being actually the second choice for the position in Shocker.
Lastly, Gel-Shocker's General Black, he was once an Army official of the former Imperial Russia. He got to the position of General while still young due to his cruel and effective tactics.
His cruel methods of torture and boldness in combat spread fear to both his opponents and the farmers of his own country. After the fall of the empire, he was approached by an esoteric Buddhist group called "Geldam". Involved with the new group, he traveled to Africa, where he continued a perfect terror campaign. He kept his old uniform and ranking from the Russian Empire.
Finally, he was contacted by Shocker's Great Leader and went to Japan, founding "Gel-Shocker" there. The medals on his chest were presented by Nicolai II himself, the Russian army and even Gel-Shocker's Great Leader.
The extensive Doctor Shinigami backstory (which includes him being part of the Nazi, his love for her sister) was found on the book written by show producer, Tooru Hirayama entitled, "My Beloved Characters" while the rest of the entries was found Japanese Wikipedia.
Also, the same /m/ thread has a back story about Kamen Rider Amazon's Garanda Empire but since most of the stories that I found are related to Shocker and Gel-Shocker, I decided not to place it. You can check it out in the link found on top of this post.