Clark Kent and Davis Bloome had a relationship that stemmed back to their home planet of Krypton. However, they only became aware of it during Season 8, when they both came closer to fulfilling their respective destinies.
Kal-El was sent to Earth by his parents Jor-El and Lara-El with the intention for him to become Earth's savior. Unbeknownst to them, the Kryptonian renegades General Zod and Faora attached a cocoon containing a fusion of genetic material taken from Krypton's most violent life-forms and their own DNA to Kal-El's spaceship to become Earth's ultimate destroyer, Doomsday. Jor-El and Zod were fierce enemies, whose battle was inherited by their progeny.
Not long after Kal-El's ship landed on Earth during the first meteor shower that struck Smallville, Kansas in 1989, Kal-El came out of his spaceship and was found by Jonathan and Martha Kent. Meanwhile, liquid hatched from the cocoon, almost instantaneously forming into a little boy who would later be named Davis Bloome. Unaware of Davis' presence, the Kents took Kal-El with them, leaving Davis traumatized, naked and alone as he watched Kal-El be taken to a happy home.
Kal-El, now known as Clark Kent, and Davis first met at Metropolis General Hospital, after Davis had become friends with Chloe Sullivan. Davis assumed that Clark was Chloe's fiancé, and it was only when Clark looked confused that Davis realized his mistake. Clark was clearly bemused as to why Chloe had trusted Davis over him with the news that she was engaged to Jimmy Olsen. The next time the two men met was when Clark was relying on Davis to save Oliver Queen after he was poisoned. Clark appreciated his help. After these initial meetings, it seemed that these two were beginning to build a friendship.
When Clark found Davis covered in blood after an attack at the Ace of Clubs, he was clearly concerned for Davis and wanted him to be checked over by paramedics, but Davis was dismissive of Clark and keen to keep to himself. After investigating the attack, Clark found out that a serial killer was on the loose in Metropolis and discovered that Davis was at the scene of every crime, which led him to suspect Davis. When Clark confronted him, Davis was confrontational and argued back that Clark was at the crime scenes as well. Immediately thinking the worst of Davis, Clark became concerned for Jimmy's safety when he found out they were spending time together. When Randy Klein was caught for the attacks, it seemed Davis was in the clear. However, Clark and Davis had a strained relationship from then on.
When Brainiac began to remove Chloe's memories, she only remembered Davis, but when Chloe came to him for help, Davis felt that she needed to be with Clark and Jimmy rather than him, putting aside his differences. Despite this kindness, Clark remained suspicious of Davis.
During Chloe's wedding, Davis transformed into his monstrous alter-ego Doomsday, but was clearly still motivated by the feelings of his human counterpart. He viciously attacked Clark, who was shocked by his strength. Unaware that the monster was Davis, Clark investigated the creature for several weeks.
When Chloe and Jimmy broke up, Clark sided with Jimmy due to his distrust of Davis, although he thought Jimmy had gone over the top with claims that Davis was a serial killer. Clark then saw Chloe and Davis preparing dinner together, much to his surprise. He wasn't happy with the amount of time that Chloe was spending with him, as he felt she should be with Jimmy.
When Clark realized that Davis was Doomsday and discovered his past, he confronted him, only to find he was trying to kill himself with kryptonite. Clark felt guilty for being the one who was saved by the Kents while Davis was left being passed from foster home to foster home. He tried to stop Davis, suggesting that they could be brothers due to their shared Kryptonian heritage, and blamed everything that had happened to Davis on himself. Nevertheless, Davis couldn't control the beast inside him and, as he was created to destroy Clark, began to transform and was about to attack when Chloe pulled the lever to expose Davis to the liquid kryptonite. Clark found this hard to watch, but was relieved that Doomsday had apparently been defeated.
Later on, Clark discovered a connection to Doomsday and a recent murder, which led him to suspect that Davis was still alive. He eventually found Davis in the Talon basement and dragged him at super speed to the Fortress of Solitude, where Clark planned to send him to the Phantom Zone where he couldn't hurt anyone again. Despite being desperate to put a stop to his painful transformations, Davis was angry that Clark should suggest this when it meant he had to face a life without Chloe, the love of his life, and couldn't understand why his Kryptonian brother would do this to him. Realizing the danger that Davis posed to the world, Clark realized that he was wrong and that they could never be brothers after all. With their hatred for each other now evident, Clark and Davis battled it out until Chloe intervened and sided with Davis instead of Clark. Chloe knew Clark better than himself, and understood that he could never live with himself knowing that the good half of Davis was trapped with his Doomsday persona in such a terrible place.
After having time to think, Clark realized his adversary was Doomsday rather than Davis, and he hatched a plan to separate the two using black kryptonite; this showed Clark's caring nature and understanding even towards someone that he did not like. Nevertheless, with Doomsday separated from Davis, Davis had already become mentally and/or emotionally unstable, as he murdered Jimmy after finding out that Chloe still loved Jimmy and had only tried to help him because she was trying to save Clark. Clark was disappointed in Davis.