The Rookie

the rookie is the main character in lego dc super villains. it is a custom character and so his/her apearence,powers,gender and even species varies depending on the player's choice : in-game this is explained as the rookie actually being a variant of the Amazo robot, meaning they can absorb powers, abilities and pretty much anything else they desire (though obviously for balance reasons this power-absorption is lower than the actual Amazo androdi).

biography
as mentioned above it is a variation of the amaso robot that  was sent on arkham asylum. later he/she broke out along with lex luthor and joined his villain group. then it and the rest of the villains discover the justice syndicate and darkseid plan to conquer the world and try to stop it