The Outer Worlds

-Flaws are typically acquired by repeating something negative many times. They change your characters attributes slightly and reward you with a free perk point.
-Flaws are completely optional and can be rejected, and although this achievement is missable, by the end of the game you will likely have encountered more than 3 phobia prompts. Flaws MUST be accepted to count toward the achievement,
-Flaws are limited to 3 on normal, 4 on hard, and 5 on supernova.
-Phobias are flaws that give you -1 Perception, -1 Dexterity, and -1 Temperament when in the presence of the source of the Phobia. (Raptidons for raptiphobia, etc.)

-Flaws appear to trigger on a cooldown, meaning, for example, Acrophobia cannot be acquired by repeated purposeful falls.

Acrophobia - Taking too much fall damage.
Cynophobia - Taking too much damage from canids.
Paranoid - Being caught committing crimes too often.
Robophobia - Taking too much damage from robots.
Herpetophobia - Taking too much damage from mantisaurs.
Raptiphobia - Taking too much damage from raptidons.
Addiction Withdrawal - Too many consumed meds.
Permanent Concussion - Taking too much damage to the head.
(Damage Type) Weakness - Taking too much (Plasma, N-Ray, Fire, etc.) damage.
Pithecophobia - Taking too damage from primals.
Physical Damage Weakness - Taking too much physical damage.
Permanently Crippled - Taking too much damage to the legs. (Crippled Status.)
Partially Blind - Taking too much damage to your eyes. (Blinded status.)
Permanently Maimed - Taking to much damage to the arms.

-It is my personal opinion that Phobias are your best choice as to not inhibit the rest of your playthrough, as they have no adverse effects outside of combat.

*If anyone has found more, please let me know and I will add them to the list.

The achievement unlocks when you accept your third flaw. The offer of a flaw is triggered when too many actions of a certain type cause harm to the player-character or when a benign action is performed excessively. The flaw is normally a permanent debuff.

The permanent debuff can be annoying. I played through the game with Corrosive Weakness (+25% Corrosion Damage) and Drug Addiction (-1 to each of perception, dexterity, & temperament unless I continuously ingested drugs to counteract it). I accepted a 3rd flaw, permanent concussion, to unlock the achievement. Following that, I reverted to the save just before triggering the flaw so I played the remainder of the game with two flaws rather than three.

Because I found it so annoying, I took a different approach when going for the equivalent achievement in the Series S|X version of the game, The Outer Worlds: Spacer's Choice Edition. I unlocked the achievement on a throwaway save--a process that took about half an hour. It's heavily RNG dependent so the time will vary substantially by player. I provide this alternate approach below. The advantage is that I unlocked the achievement but then continued the game with no flaws and their negative consequences.

The player can refuse any flaw and continue the game without consequence. Alternatively, the player can accept the flaw and incur its negative consequences. If the flaw is accepted, the player receives a bonus perc. The achievement pops when the 3rd flaw is accepted. Rejected flaws do not count towards the achievement.

There are over two dozen flaws in the game. I am aware of 29 that I have listed in a Google Docs spreadsheet. The spreadsheet provides the name of the flaw, its adverse consequences, a description, and how it is acquired. It can be seen at this link: https://tinyurl.com/List-of-Flaws

The number of flaws that can be accepted is dependent on the difficulty setting:

• Normal Difficulty - 3 Flaws
• Hard Difficulty - 4 Flaws
• Supernova Difficulty - 5 Flaws

26 July 2023 Edit: Playing the Spacer's Choice Edition, @JelmerF, confirmed that the 3 flaws can be accepted on story mode. Presumably, the same applies to this, the original version of the game.

Once a flaw is accepted, it and its negative consequences are permanent. However, the player can load a save made prior to accepting the flaw(s). I do not know what happens when a player on supernova difficulty acquires 5 flaws and changes the mode to normal. I don't know if the 5 flaws carry over or if the number of flaws is reduced to 3. Please make a note in the comments if you know.

Flaws related to a particular type of damage--shock, plasma, N-Ray, & corrosive--are, in my opinion, the easiest to endure. The player-character incurs 25% extra damage. The negative effect is limited to the occasions when that type of harm is encountered. Permanent decreases to stats & attributes are far more debilitating. They may result in lower dialog skills, hacking, lock-picking, and other skills that are important in advancing the game's story.

The game's flaw prompt is random. It has a very small probability of appearing every time the trigger occurs. For example, every time the player-character falls or jumps from an elevation high enough to inflict damage, one of two flaws might be offered: acrophobia and permanently crippled. (Note that the permanently crippled flaw can also be triggered by frequent injury to the legs in combat.) The more times falls and jumps result in damage to the player-character, the greater the likelihood of the flaw being offered. It can be refused and should be for the worst of the flaws.

Permanently crippled reduces mobility (walking & sprinting speed) by 30% and removes the ability to dodge. It is very tedious going through the game at such a slow pace not to mention that enemies have a substantial speed advantage. Thus, permanently crippled is one of the most debilitating flaws in the game.

Recommended Approach:
My recommendation is to unlock the achievement on a throwaway save file early in the game before leaving Emerald Vale. The enemies are at a much lower level than those encountered later and it's easier to absorb the harm that will trigger the flaw.. Unlocking the achievement on a throwaway file ensures the player can enjoy the game without the additional impediments the flaws bring to the table. Of course, if you desire the challenge of playing with flaws, you can use the method below and continue the game without reverting to an earlier save file.

Play the game normally on the difficulty of your choice. Save frequently. If on supernova, you can only make manual saves in your ship so bank auto-saves when the opportunity arises--going into Edgewater, the Community Center, etc. When the flaw prompt appears, accept it. Fast travel back to your ship and make a manual save. If the save made just prior to the flaw was an auto-save, load it. Fast travel to your ship and make a manual save. Make note of this save for it is the one you are going to return to following unlocking this achievement.

Load up the save file made after accepting the flaw. If playing on a difficulty other than normal, change the difficulty setting to normal. If you have a free slot in your inhaler, put a type of food in it. If you have a second free slot, put some kind of drug in it. Don't worry if you are playing on supernova because, after unlocking the achievement, you will return to the supernova save file made before accepting the flaw. Exit your ship. To your right front are three primals. If you have previously killed them, sleep for 24-48 hours and they will respawn. Make a manual save before engaging them being careful not to overwrite the save you intend to return to after the achievement. Also don't overwrite the save file you made upon acquiring the one flaw. You will return to it if you run low of Adreno before triggering a flaw.

After saving, direct your companion(s) to a safe point. Engage the primals by getting their attention but do not attack. Instead, heal liberally.with your inhaler. Note that the they may be asleep or awake. If asleep, they will wake up to attack you. Primals inflict physical damage, concussions, and N-ray damage. All three of these can result in flaws. Fighting primals can result in the Pithecophobia flaw. Finally, food &/or drugs in your inhaler can result in food and drug addiction respectively. Check your status on the upper left of the screen. Once you see the icons for concussion and N-Ray damage, proceed back to your ship healing as necessary. Sleep for any interval and engage the primals again without attacking them. If you get low (20 or so remaining) of adreno, load up the save file with the flaw that was made before engaging the primals.

When the flaw prompt appears, accept the flaw. It should be your second. Return to your ship and sleep. Make a manual save. Do not overwrite this save. You will return to it in case you exhaust your supply of Adreno. This will be your 2-flaw base file. Exit the ship and fast travel to the community center. You will find yourself across the street from the community center and elevated with respect to it. Cross the street. Keep the community center to your right and walk forward until you come to a rocky ridge blocking your way. Keeping the ridge to your right, turn left and follow it down an incline into the Primal Nest. It will appear on your map if you previously discovered it. If not, you will get XP for discovering it at this time.

The primals can either be asleep or awake. Either way, direct your companion to a safe place and make a manual save before engaging them. As before, be careful not to overwrite the save you intend to return to after the achievement. Engage the primals in the same manner as the ones outside your ship. Fast traveling to a new location increases the probability of triggering a flaw--hence the trip to the Primal Nest. Heal liberally upon engaging the primals. Once you've been afflicted with a concussion and N-ray damage exit the primal nest the way you came healing as you go.

When exiting, you can go on top of the ridge that you followed while going to the primal nest. Go on top of it and follow it until you can look down on the community center to your right. You will see some scrap metal below you. Jump or fall onto it. You will incur damage with the possibility of triggering the acrophobia and permanently crippled flaws. Overwrite your insurance manual save (the one made just before engaging the primals and not the 2 flaw base save file you made in the ship). Optionally enter & immediately exit the back entrance of the Community Center. I believe the loading process increases the chance of triggering a flaw. Return to the primals and continue repeating the engage primals/incur damage from fall loop until you get your final flaw. Keep tabs on your inhaler to ensure you have either food or drugs if slots are available. Also keep track of your adreno. Before it runs out, reload your 2-flaw base file and restart the sequence in the Primal Nest.

The next flaw triggered will be your third. Accept it and the achievement will pop. Load up the save you made before accepting the first flaw. If you were playing on supernova, you will note that this save file has the supernova denotation. Continue with your game. The manual save files you made while pursuing this achievement were throwaway files. Delete them taking care not to accidentally erase valid files. You are now free to progress in your game and can reject all flaws that might be offered to you in future.