Fight another 50 duels, with player 1 winning them all for 166 more Badass Ranks. Save and quit, then start another new game, creating another new character for player 1 (don't bother messing with player 2's character). To build a high Badass Rank, and gain all the perks associated with it, create a pair of new characters in co-op mode and have player 1 beat player 2 in 50 duels. The only thing you need to worry about is the flame cyrstalists since they can and will knock you into the lava with one of their attacks. You also do not need to worry about getting to higher ground when the lava rises since the lava can't reach you. But if the warrior pops up beside you, take cover behind the pillar and his fire breath will not hit you. If you go under the shelter, the warrior cannot reach you with any of its attacks (providing its on the side opposite to the shelter) so you can just unload bullets into the thing.
When you first enter the area, go to the place where Jack and Lilth would be and off to the left is sheltered area with a ammo deposit behind it. Related: Borderlands 2 Review Secrets The Warrior Trick Repeat as desired (for faster duplication, transfer all copies of the item to player one, save-and-quit with both, and start over with the duplicates on player 1). Because the game doesn't save player 1 when player 2 leaves, nor when you quit from the system menu, now both players have said item(s). Give desired item(s) to player 2 and have player 2 save and leave game. Start a two-player co-op game with the first character as player 1 (and the other character as player 2, obviously). Place the desired item(s) on a character, and ready or create a second character to take on as many of the item as you wish. Go to the slit machine at Sanctuary and shoot the middle slot and you will get a legendary gun. Under gameplay it will unlock extra wub, but sorry, it does literally nothing. To unlock extra wub, go to the title screen(where it says push start) and do the konami code, up up down down left right left right O X start. Check out our 10 Tips for Borderlands 2: A Vault Hunter's Guide and our Mechromancer Skill Tree Tips and Analysis.