The Borderlands 2 end boss fight is long rather than difficult once you find the perfectly safe spot on the map. Your only risk is leaving it to grab more ammo. To help you rally in case of catastrophic misadventure, the boss fight includes an endless swarm of rakk. If you get knocked down, shoot one, and you’re back. Your main threat there is falling down so often that you do not have enough “fight for your life” time to shoot a rakk.
Playing as the Mechromancer, her pet robot contributes to the fight oddly. With the talent tree I was using, the robot could one-shot rakk to add 5 seconds to its battery life. It did so every 3-4 seconds. Instead of fighting the boss, it sat there farming, and it did so endlessly unless the boss accidentally AEed it out of existence. Free xp and money, scattered loot and ammo, auto-rez: everything you want except a meaningful contribution to the fight. That’s okay, I had it under control.
That endless rakk swarm does not stop spawning with the boss’s death. The rakk only occasionally hit the robot, so it just kept farming them as they flew by. I watched for a while, amused. I wandered around and picked up loot. I explored the area. Once it got around 200 kills, I activated the game’s ending. The robot was still farming rakk in the background of the cut scene. I watched the credits. When they ended, the robot was still farming rakk, and it had been doing so the entire time the credits were rolling. I leveled. I watched for a while, amused. I threw away less valuable loot and picked up better drops. I went to the bathroom, considered making a sandwich. The robot had 500 kills and was still at half health. I quit because I wanted my computer back, but I’m guessing you could get to the level cap just by leaving it running with a macro to hit F occasionally in case the robot dies.
Of course, at that point, just edit your save file.