Injustice: Gods Among Us

This is going to take a LOT of your time and patience, so be warned. However, I know exactly how to do it and it is simply a matter of how much time you have on your hands. Here's some general info:

You can do this entirely on your own, all you really need is a second controller.

There are 6 sections to the Archive, and two of them are fully unlocked by default. The other four require 84 Access Cards and 24 Armory Keys. Assuming you're also going for Level 100, you'll eventually have what you need since you unlock both through leveling up. I unlocked the final Access Cards around level 70.

I strongly suggest playing through Story, beating the STAR Labs, and finishing all of the Battles before doing this. You level up in all of them and won't have as far to go. I used this solution to start grinding XP, and it works like a charm. You'll gain about 50k XP every 15 minutes.

Contrary to Templar Punk's solution, you can use a turbo controller with this method and not have to worry about characters glitching, so you can do this overnight without any trouble. You also only need to turbo RB with my solution, leaving less room for glitching. Despite being a few frames slower, you're really only shaving a few minutes off the time per hour, so it's not that big of a deal considering you'll be sleeping anyway.

My video will explain the rest of the process while showing you how to do it. By the way, this will also build towards Gonna Need A Bigger Closet and The Hero We Deserve. If you have any questions or anything to add, leave a comment and I'll do what I can.

Select Bonus Features -> Archives from the main menu. Here, you can use access cards, and armory cards that you've earned through leveling up to unlock extra content in the game.

What you'll need to unlock everything:
Extras - 21 Access Cards
Concept Art - 37 Access Cards
Music - 26 Access Cards
Costumes - 24 Armory Cards

How to get cards:
Level 1-50 - 1 Access Card per level
Level 51-75 - 2 Access Cards per level
Level 75+ - 3 Access Cards per level
Armory Cards - One every two levels

Provided you don't spend any cards on XP Boosts, you can have everything and unlock this achievement by level 68.

You earn XP and level up after completing matches in almost any of the games modes. If you're going for most of the other achievements, that should give you a decent head start. If you need it, here is a fast, easy way to farm XP:

**FASTER TURBO CONTROLLER METHOD** (possible to do it manually too)

This method can earn you massive amounts of XP points, especially overnight with very little effort if you have a turbo controller (still possible to do manually). This will help you unlock all the items in the Archives relatively easy.

1. On the menu go to game settings. Turn the timer off.
2. Go back to the menu and select Multiplayer. Then select Versus.
3. On the character select screen, press start on controller 2 and pick Flash for both players (or any character that does similar interactions).
4. On the stage select screen, go highlight the Hall of Justice. Switch the starting point (press Y) to the Great Hall.
5. When the match starts, have both players go to the right of the screen until you see the mini space jet floating on the upper part of the screen (that you can glide on).
6. Have Player 2 go to the right of the mini-jet and have Player 1 right under it.
7. Now if you have a turbo controller, set your interact button on turbo. Now tape/ rubberband the analog stick up to have Player 1's character jump up continually. Now tape/rubberband the interact button and voila way faster. Since you are continually interacting with the object the points will add each time you do it.
8. When you are ready to come back to the game after idling or not. Just make sure you finish the match with Player 1. DO NOT QUIT OR YOU WILL LOSE ALL YOUR POINTS!

This method seems to be a lot quicker since there are less frames to interact with the object (mini space jet) compared to Cornerscout's video in the Atlantis stage. You can probably save an hour or two depending on how long you do it, especially overnight. This is also possible to do manually but seems more tedious than the other method since you're also pressing up to jump, but still way faster.

Make sure you pick up a 5x multiplier!!! It definitely speeds things up!!!

*Update*
-There's been some talk about Flash glitching and not coming down from the interaction. Make sure to check your screen every few hours to see if he is okay. You can use Player 2 to knock him off the glitch. To be honest, it never happened to me so I wouldn't worry too much.
-Just got the achievement! It took me around 20 hours and the 5x XP bonus multiplier helped big time!

**Credits go to dalleval from youtube for the video**

Happy idling!