In LEGO City: Undercover, Rex can be unlocked near the end of the final mission of the game and is worth a million studs.
Rex might have came from a 'rough' family, given the fact he was a criminal since he was six years old.
Given the fact Natalia testified against him, he shows no signs of hatred towards her.
In the 'The Chase begins' when Gleeson was showing 2 pictures of him, he appears to be playing with a dog which indicates he must have a soft side for dogs.
His space suit is unlocked by "conquering all districts".
It's still unknown why he sent his goons to Vinnie Pappalardo to 'deal with him', although it is assumed that he did it since Vinnie told Chase and Moe to steal things from Forrest Blackwell against Rexes commands.