Doomsday is a seemingly unstoppable behemoth who adapts to overcome and destroy anything or anyone in his path, Doomsday is most famous for being the murderer of Superman. He is the result of Kryptonian genetic engineering gone awry.
After Pete Ross lost his senate position, the couple (Pete and Lana) returned to Smallville. Later, Lana became pregnant, and involved in a car accident, which caused the baby was born 2 months pre-mature. She called Clark to ask him if he could help save her baby. As Superman, he was taking the infant to another hospital when Doomsday, inhabited by Brainiac's mind, attacked him. He took the child, intending to grow a more controllable Doomsday from his tiny body. Superman and the child's father, Pete Ross, rescued the infant and Brainiac's technology had made him healthy. Lana and Pete named him Clark Peter Ross (Superman: The Doomsday Wars #1-3).