Sadaharu Kinniku

The younger brother of Tatsunori Kinniku, Sadaharu Kinniku started out life into the royal Kinniku family. He possessed a genius wrestling ability and believed himself to be superior to his brother. At the mere age of thirteen, he unconsciously performed the Muscle Spark, which killed his sparring partner in the process.

He was thus locked away in an underground dungeon and his existence erased from history. After receiving the death sentence, he escaped from prison to Mt. St. Parfait where he faced off against Mirageman. Recognising Sadaharu as the descendant of Silverman, Mirageman invited him to become reborn as the Perfect Chojin Nemesis.

(Source: Kinnikuman Wiki)