This achievement will unlock once the credits start rolling.
There are four main endings to Cyberpunk 2077 - The Devil, The Star, The Sun & Temperance. This guide will outline the quickest way to net all four endings and their respective achievements in a single playthrough.
SPOILERS FOR THE GAME BELOW!
Firstly, there are some prerequisites for unlocking certain endings that you should be aware of:
During the main mission 'Search & Destroy', you will be in a dilapidated apartment building with Hanako & Takemura. Arasaka forces will attack in a scripted sequence and you will fall through the floor. Your objective will be to escape the building, but you will need to rescue Takemura here. Once you regain control, head through the first two doors, then there should be a hole in the wall on the left you can crouch through, you can then head upstairs and kill the enemies. You will have done it correctly if he appears when you leave the building and tells you to split up. This will ensure that 'The Devil' achievement unlocks during one of the endings later.
You will also need to complete Rogue's side questline in order to forge an alliance between her and Johnny to unlock 'The Sun' ending. After the main story mission 'Tapeworm' you will wake up in a hotel in Pacifica. Johnny will want V to call Rogue. Do so, and you will start the quest 'Chippin' In'. During this quest, you will visit Johnny's grave. You want to choose the following dialogue options here:
“The Guy who Saved My Life” > “Nah, fucked that up too” > “What do you want from me?” > “OK. But as second chances go, this is your last.” > “You were a real dick in the beginning” > “When you said you let down your friends…” > “Smasher biz really got to her.” > “Yeah, I’ll call Rogue.”
This will unlock the second part of the questline, 'Blistering Love' and ensure you can use her for the finale.
The final prerequisite is the completion of Panam's questline, which will unlock following the main story mission 'Life During Wartime'. Complete the missions Riders on the Storm > With a Little Help from my Friends > Queen of the Highway. This will see V get closer to the Aldecaldos and you will be able to use her for the finale.
The choice of what ending you get is decided by one conversation in the mission 'Nocturne Op55N1'. When you get to the rooftop and have to sit with Misty, make a manual save that you can easily revert to.
The first ending involves trusting Arasaka to remove the biochip, much to the disdain of Johnny.
You want to pick the following dialogue options:
"Think trusting Arasaka's risky but worth it" > [Take Omega Blockers] "Yeah, don't be mad."
This will lead to the ending quests Last Caress > Totalimmortal
If you saved Takemura during 'Search and Destroy' then the achievement should pop after talking to Yorinobu and entering the elevator during 'Totalimmortal'. This then leads to the epilogue 'Where Is My Mind?'.
Now reload your manual save from the rooftop.
These endings can be done at the same time. During the conversation with Johnny, pick the options "Think you and Rogue should go" > [Take Pseudoendotrizine] "I am. Do your thing, Johnny."
You will let Johnny take over your body and will assault Arasaka Tower with Rogue during the ending quests For Whom the Bell Tolls > Knockin' On Heaven's Door.
Following the boss fight with Adam Smasher, make a new manual save so you can get both endings with minimal replay.
Now when you are talking to V and Alt in cyberspace you will make the decision for these endings. Choose to cross the bridge into cyberspace and you will get 'The Sun' ending with the 'Path of Glory' epilogue. If you enter the well and return to your body you will get the 'Temperance' ending with the 'New Dawn Fades' epilogue. Reload your save after you defeated Adam Smasher once you finish one in order to get the other.
There is also another option to get both of these endings without Rogue. If you picked the prerequisite options during 'Chippin' In', during the conversation with Johnny get to the part when you choose who you are going with, then do nothing for 5 minutes. This will trigger additional dialogue where Johnny invites you on a suicide run through Arasaka HQ. Choose 'Let's hear this plan' > [Attack Arasaka Tower] "Means goin' out with a bang, I like it." This will lead to the ending quest (Don't Fear) The Reaper, where you attack Arasaka Tower solo. If you die during this run, the game will end, and you will fight much tougher enemies, but if you reach the end you can enter cyberspace for the 'Temperance' ending or climb into the well for 'The Sun'.
Now reload your save from the rooftop again.
In this ending, you will mount the assault on Arasaka Tower with help from Panam and the Aldecaldos, then leave Night City forever.
During the conversation with Johnny, choose "Gonna ask Panam for help" > [Take Omega Blockers] "Yep. Gonna do this with the nomads."
This will lead to the ending quests We Gotta Live Together > Forward to Death > Belly of the Beast.
Once you are in cyberspace, choose to enter the well and return to your body to get 'The Star' ending. If you enter cyberspace here this is another way to get the 'Temperance' ending. Getting 'The Star' ending will lead to the 'All Along the Watchtower' epilogue.
That is all of the endings that relate to achievements. There is one more ending, however. Once you choose an option (Arasaka, Panam, Rogue) during the conversation with Johnny, choose the option "Could also just put all this to rest" then [Toss Pills] "I know. Exactly what we're gonna do." This results in the game ending right there, with a pretty dark ending.