The loot collecting aspect of Injustice 2 adds a whole new way to play the game, giving the player some extra incentive to complete the plethora of single player challenges on offer. (useapotion.com)
You can visit the vault which offers single player challenges as you pick which monster to play and must beat a certain amount of enemies. (switchera.net)
Also included are 45 single player challenges which will unlock content as players complete them. (xblafans.com)