Borderlands 2

So this is the most grindy achievement of bl2, its easiest with the character you played most with and you get it by unlocking all lvl 1 challenges.

Some of the hardest ones are:

Blue Sparks (Vehicle): There is a big chance you haven't made any progress in this section, understandable, I had the same after doing all my playthroughs. To get these you need to power slide over enemies. To do this you use the handbrake and turn the vehicle towards enemies. Here is a bit more explained how to do it: tutorial on powersliding by SheDevil

JEEEEENKINSSSSSS!!! (misc): Kill Jimmy F****** Jenkins, there are a few methods online and having tested quite a few I can say with confidence that having the Mission octers Orders active, then going to wildlife resort until you reach the room with the 4 small boxes WITHOUT taking the mission objective, is probably the fastest. To speed up the grind a bit you can go in the wildlife Annex (the arena) if you have the dlc for faster Save and Quit reloading. HappyThumbsGaming detailing the method

#Hidden challenges:

Catch-A-Rocket (hidden): To unlock this one you have to complete the level 5 challenge of Splish Splash, it is pretty grindy. My best advice would be to go to an area with a lot of enemies and fire away with a high magazine size rocket launcher (preferably on normal difficulty for that sweet one shot). Once you complete the lvl 5 challenge there is a big chance that the first few levels will unlock automatically since it already counts your progress from before unlocking it.

Shotgun Sniper (hidden): Analogue but now you need lvl 5 Open Wide, this one is a bit more tedious as process will be slower if you played a character where you didn't use shotguns that much.

There are of course plenty more challenges but these were the ones giving me the most trouble (F*!,lk, Jenkins...)

If this guide helped you or you are having trouble with another challenge feel free to send me a message and I will try to adapt this as soon as I get the time!

IMPORTANT: I didn't mention it above but you do NOT need all challenges listed, with non level specific they mean areas, all challenges regarding finding all the vault symbols are not required aswell as the DLC challenges these are not needed aswell.

There are already lots of great guides for strategies during the boss fight itself, but here's another bit of info that will make this extremely easy.

Complete the "Fight For Sanctuary" DLC with True Vault Hunter mode and receive the Toothpick (Assault Rifle) and Mouthwash (Relic) effervescent items as part of the story quests. Under TVHM, these will match your current level.
Then return to Normal mode and complete the DLC again in order to start the Haderax mission. In Normal Mode, Haderax will max out at level 40, making it extremely easy to kill with your overpowered effervescent items.

Visit all the "greyed" out areas of all the different locations in the Pirate's booty DLC.

These areas include: Hayter's Folly, Oasis, Wurmwater, The Leviathan's Lair, The Rustyards, Magnys Lighthouse and Washburn Refinery.

The most common one that people have not gotten is at Magnys Lighthouse. At the far end of the map there is a "Secret Stash" wich is a small room inside a building. Go there and you will get a pop up notifying you that you have found a new place on the map.

If you have looked everywhere and still haven't gotten the achievement i would recommend this site: https://borderlands.wikia.com/wiki/Category:Captain_Scarlett_and_Her_Pirate%27s_Booty_locations

It gves you a lot of usefull information about the area in hand and can help you towards getting the achievement!

Hope this guide was helpfull and that you are one step closer to completing Borderlands 2!