Injustice: Gods Among Us was a fantastic game with a great story to tell. That game did, however, pick up halfway into the story. A lot of Superman’s rise to power and the escalation of world affairs was left a mystery, but recently all of those mysteries were solved in the comics. The Injustice comics covered the five years between the events that set Superman on his violent path, but if you aren’t interested in catching up on everything, here are a few breakdown videos from History Behind the Warrior.
Year 5, the final year before Injustice: Gods Among Us, is missing from these breakdowns, but will likely be uploaded soon so keep an eye on his channel. As for Injustice 2, he has uploaded this next video compiling everything we know about the story of Injustice 2 so far, including a bit of speculation on characters and allegiances.
Source: History Behind The Warrior