Borderlands 3

Most of this achievement shouldn't be an issue and if someone wants to provide a full solution for me to edit into this one or make their own, go for it.

But, the most likely to be a problem location is the sign next to a waterfall in the Primeval Grotto (Floodmore Basin) near one of the ancient writings:
https://clips.twitch.tv/TastyEnjoyableBasenjiAMPEnergy


Edit: Some people have had issues where even though they did have every location, it did not work. These people have also had success in getting it in their TVHM mode once completing the requirements again.

"I've been going through getting these achievements, followed that theory that if you go to sanctuary, turn off revenge of the cartels and mayhem mode then save and quit they'll unlock if you visit all the locations in one go (making sure to not go back to sanctuary). Has worked a treat." - Punderstatement

Yeah you can go to other guides for the locations but that's what you came here for … here they are:

Eden-6
• Jakobs Estate: 10
o Leery Hamlet
o The Unhollowed Blog (Side Mission: Witch’s Brew)
o Servant’s Lift
o Grotto
o Jakob’s Manor (*press button on trolley lift to get up there)
o Welcoming Chamber
o Archives
o Ancestor’s Hall
o Theater
o Monty’s Den

• Ambermire: 10
o Ambermire
o Rogue’s Hollow
o The Moist Hoist
o Soggybog Rigs
o Highground Folly
o Mirefall Rigs
o Tig’s Big Rig
o The Mudneck’s Hideout
o Delvin’s Dock
o Curltail Warren (Side Mission: Raiders of the Lost Rock – accepted from Claptrap in Sanctuary)

• The Anvil: 7
o Hector’s Lament
o West of Gross
o The Yard
o The Devil’s Saucepan
o Shankland (Side Mission: On the Blood Path)
o Central Security
o Ultramax Spire

• Voracious Canopy: 11
o The Green Labyrinth
o Wreck of the Family Jewel
o Outer Hull
o Cargo Hold
o Distribution Corridor
o Security Bay
o Private Shuttle Bay
o Bridge of the Jewel
o Science Outpost
o The Terradome
o Kingdom of Bobo the Great

• Floodmoor Basin: 15
o Hangman’s Garden
o Reliance
o Lumberhold
o The Timbermills
o Primeval Grotto
o Jason Waterfalls (*requires very specific positioning under waterfall)
o Dead Man’s March
o The Witch’s Peat
o Headlift
o Knotty Peak
o Fort Sunshine
o Lumberton Junction
o Mudhaven
o Slickhouse Garage (*requires very specific positioning)
o Lonesome Isle (Side Mission: Get Quick, Slick) – during this side mission you get a special car that you have to jump over a big ramp to this hill

• The Floating Tomb: 2
o Altar of the Guardians
o Vault of the Graveward (*No Map Data Available – enter the purple portal after defeating Vault boss)

• Blackbarrel Cellars: 8
o Premium Casks
o Norton’s Study
o Gunpowder Mill
o Forgotten Halls
o Copperstill
o Estate Gardens
o Observatory Grotto
o Neglected Solarium

I just had issues unlocking this myself so here's some help. Obviously check Jason's Waterfall because it's a dumb location. Also check the Devils Saucepan, Security Bay and The Terradome because despite standing in them it took some finagling to trigger the name. Lastly The Lonesome Isle you can blue out the island from below but unless you make the jump you won't get the name to trigger.