Earth-2 was a parallel universe that co-existed as one with the Earth native to Clark Kent's universe.
Ultra Man is Earth's 2 evil Superman. Clark of Earth 2 is named is Clark Luthor. At that reality Clark was found by Lionel Luthor instead of the Kents and he was raised at the Luthor Mansion alongside Lex and Lutessa Luthor. Lionel had Clark to kill Lex and wanted him to become his heir. Clark Luthor was way more darker than Clark Kent and he terrorize the Metropolis and killing anyone who would oppose him. At season 10 of Smallville Clark Kent and Clark Luthor switched places. At the other Earth Clark learned that Lois and Oliver are engaged. Also Lionel of that reality told him Oliver Queen has the mirror box the device he wanted so as to return home. At the end Oliver and Clark meet at the Watchtower buliding and Oliver traps Clark with kryptonite and prepares to kill him but Lionel hits him over the head and reveals that he had the mirror box the entire time. At this point, Oliver realizes that Clark is the "good one" and turns off the kryptonite and the inccident is solved. In Metropolis Oliver has called a press conference to reveal that Ultraman is really Clark Luthor and to announce that Queen Industries is going to provide every citizen of Metropolis with a personal amount of "meteor rock" with which they will be able to defend themselves from the villain.