Dragon Ball: Superman is invincible, so why bother with Saiyans?

Story of: Dragon Ball: Superman is invincible, so why bother with Saiyans?(This book is slow to pick up, and the protagonist will not be invincible at the beginning.) Heaven has traveled through time. He was originally a Kryptonian, but due to the turbulence of time and space, he traveled to the Dragon Ball world. At the beginning, he was captured alive by the Red Ribbon Army and became the material for human experiments. He did not suffer any harm. Sunshine, he had no power to resist at all, just when he felt desperate.The strongest sign-in system is awakened. Sign in at the beginning and get the legendary Saiyan bloodline. Superman is also invincible, so why bother borrowing Saiyans again?……………………