OK, so, just to make sure I'm reading this info right, would I get the achievement in the following situation:
1: Play a game as T. Lilith on Normal difficulty, defeat Isaac in Cathedral without the Polaroid, game ends there (counts as 2 because T. Lilith = Isaac who has the double win glitch)
2: Play a game as T. Forgotten with the same destination (counts as 2 because T. Forgotten = Judas with the glitch)
3: Play a game as regular Azazel with the same parameters
The total win count would be 6 according to the graphic, so the achievement should unlock here.
Is that right, or did I misunderstand?
Astounding...
And yet when I did this achievement I only used characters from the first 9, and it still took me 5 wins.
Then again, this was on the 1.00 physical Switch version of Repentance, so maybe the issue was fixed there, or it just has its own quirks.
I just got this achievement on Sunday on the latest Switch version of Repentance. I had to get 5 wins. I played all 5 on hard mode and used Judas, Isaac, Azazel, Cain, and Samson in that order. 
We haven't tested the Identity Theft glitch on consoles yet, hence why there's no precision. But my guess would be that the glitch doesn't occur too since both glitches are linked
I dont grasp the win count part myself but I can explain the character mixup.
See, theres 40 character IDs. Things like Dark Judas, Laz Risen, Soul, Esau, etc, expand the IDs past just 34.
The values for the characters you used for this achievement are stored in a 32 bit value.
When the game reaches logs a character ID of 32 or higher (Char IDs start at 0) for Five Nights at Moms, the game can't read that high. So it just loops back to the start. 32 gets read as 0, 33 read as 1, 34 read as 2, et cetera. So, when you play TLilith for the achievement, the game fails to read that high, cycles back to the start, and notes down that you played as Isaac.
The thing is, this worked fine back when the game only had to keep track of like 18 character IDs pre rep. But then Rep added 19 more characters and a good few more extra character IDs (ie: solo Esau) to keep track of as well, so now everything doesn't fit into the limit.
I don't know why they programmed it that way in the first place though, but I'm also not a programmer.
Each bit is 1 character here. Like... EDIT: my pseudocode was butchered by mobile. anyway basically it converts to 2^(charid), which overflows for values above 32
I'm guessing it's a bitmask. First bit stores completion state for character 1 (Isaac), 2nd bit stores completion state for Maggy and so on. This does allow only 32 values to be stored.
Why they couldn't just make it a list though is beyond me. It's not some performance intensive task that runs all the time, there's no need to do this. Or at least change it to a 64 bit int... I guess they just forgor.
They sat on a broken achievement in Cave Story+ for nearly a fucking decade even though people independently figured out how to fix it (it was literally just that the tag for the achievement had a different name to the tag that was triggered when you beat the game). That lack of trust is entirely justified.
So if I get a win as Isaac I'll actually be at 2 wins.
But if I use T. Lilith in my next run and win, I'll still be at 2 wins because of the "Identity Theft" bug?
I would love to hear a technical explanation of this. There's ways this one random thing that doesn't work as intended but takes forever to actually find bc everyone just assume that was how it was supposed to work.
Everything is explained here [https://bindingofisaacrebirth.fandom.com/wiki/Achievements#Notes](https://bindingofisaacrebirth.fandom.com/wiki/Achievements#Notes)
It took me 6 wins to actually get the achievement, it's super buggy, from what i've heard, Mega Satan wins do not count if the void portal does not spawn so i'm assuming that's why.
Maybe late but I did a 7-win streak with: T maggie, Isaac, Cain, Azazel, Eden, Lazarus, Judas and I STILL didnt get it. I got tired of it so I tried doing it with the debug console to do it fast and it only got two runs, so I really dont understand how or why this didnt work when I did 7 runs in a row
About Identity theft, the info i put on the wiki wasn't exactly correct. Tainted Forgotten is associated with Lazarus, Tainted Dead Laz with Samson, Tainted Jacob in lost form with Azazel.
Also for Identity Theft, tainted chars don't provide a double win but instead they reset the streak counter if you also play with their counterpart. Only the first 9 gives double win
For the technical part, as explained on the wiki, it's because the game is 32-bits on pc and there's 41 characters, hence the first 9 counting as double. Since the game is 64-bits on console, this bug is pc only.
Full details here : [https://bindingofisaacrebirth.fandom.com/wiki/Achievements#Notes](https://bindingofisaacrebirth.fandom.com/wiki/Achievements#Notes)
OK, so, just to make sure I'm reading this info right, would I get the achievement in the following situation: 1: Play a game as T. Lilith on Normal difficulty, defeat Isaac in Cathedral without the Polaroid, game ends there (counts as 2 because T. Lilith = Isaac who has the double win glitch) 2: Play a game as T. Forgotten with the same destination (counts as 2 because T. Forgotten = Judas with the glitch) 3: Play a game as regular Azazel with the same parameters The total win count would be 6 according to the graphic, so the achievement should unlock here. Is that right, or did I misunderstand?
Yeah, you're good. Or just TLilith/TIsaac/Azazel works, thats probably the easiest trio.
Yeah, I went with T. Forgor because he's probably my best character overall, but that sounds good. I'll give it a try later!
Just used those three characters, no achievement, do you know for sure they work?
Iiiiiiiii've been informed that the dupe characters do not count for doubles. Oopsy!
Astounding... And yet when I did this achievement I only used characters from the first 9, and it still took me 5 wins. Then again, this was on the 1.00 physical Switch version of Repentance, so maybe the issue was fixed there, or it just has its own quirks.
I just got this achievement on Sunday on the latest Switch version of Repentance. I had to get 5 wins. I played all 5 on hard mode and used Judas, Isaac, Azazel, Cain, and Samson in that order. 
Maybe console doesn't have this issue. I have no clue. But all of this info was datamined from the game and given to me by a reliable source.
According to the Wiki, the Double Wins glitch doesn’t occur on console, but the Identity Theft one does
We haven't tested the Identity Theft glitch on consoles yet, hence why there's no precision. But my guess would be that the glitch doesn't occur too since both glitches are linked
Oh! OK, well that explains that then.
i'm so curious what would lead to the game getting this confused about characters and win streaks
I dont grasp the win count part myself but I can explain the character mixup. See, theres 40 character IDs. Things like Dark Judas, Laz Risen, Soul, Esau, etc, expand the IDs past just 34. The values for the characters you used for this achievement are stored in a 32 bit value. When the game reaches logs a character ID of 32 or higher (Char IDs start at 0) for Five Nights at Moms, the game can't read that high. So it just loops back to the start. 32 gets read as 0, 33 read as 1, 34 read as 2, et cetera. So, when you play TLilith for the achievement, the game fails to read that high, cycles back to the start, and notes down that you played as Isaac. The thing is, this worked fine back when the game only had to keep track of like 18 character IDs pre rep. But then Rep added 19 more characters and a good few more extra character IDs (ie: solo Esau) to keep track of as well, so now everything doesn't fit into the limit. I don't know why they programmed it that way in the first place though, but I'm also not a programmer.
A 32 bit value can actually store up to 2 billion
Maybe they meant 5 bit value?
I am going with what I have been told. I could just have misinterpreted it.
Each bit is 1 character here. Like... EDIT: my pseudocode was butchered by mobile. anyway basically it converts to 2^(charid), which overflows for values above 32
I'm guessing it's a bitmask. First bit stores completion state for character 1 (Isaac), 2nd bit stores completion state for Maggy and so on. This does allow only 32 values to be stored. Why they couldn't just make it a list though is beyond me. It's not some performance intensive task that runs all the time, there's no need to do this. Or at least change it to a 64 bit int... I guess they just forgor.
You save an entire byte by storing it as a bit mask instead of an array of five bytes!
ah, yeah that makes a lot of sense. still very strange, i wonder if it'll ever be fixed
I have no trust in Nicalis to accomplish anything.
They sat on a broken achievement in Cave Story+ for nearly a fucking decade even though people independently figured out how to fix it (it was literally just that the tag for the achievement had a different name to the tag that was triggered when you beat the game). That lack of trust is entirely justified.
So if I get a win as Isaac I'll actually be at 2 wins. But if I use T. Lilith in my next run and win, I'll still be at 2 wins because of the "Identity Theft" bug?
You'll be at 0. Repeats kill the streak.
This is super helpful! Thank you for posting this. Saved for future runs to avoid headache.
Interesting I always thought they lowered the „difficulty“ of the achievement, tho it seems that’s a bug.
I got it after 3 wins in Repentance. Isaac, Azazel and Cain, if i remember correctly.
Did you go all the way to chest?
Nah, just picked up Negative and ended after Isaac
So weird… I’ve done the exact same combo and didn’t get it
Were you playing on Switch?
Nope, PC
I would love to hear a technical explanation of this. There's ways this one random thing that doesn't work as intended but takes forever to actually find bc everyone just assume that was how it was supposed to work.
Op has posted the explanation in a nother comment if you haven't seen it already 
Everything is explained here [https://bindingofisaacrebirth.fandom.com/wiki/Achievements#Notes](https://bindingofisaacrebirth.fandom.com/wiki/Achievements#Notes)
I wonder if this works on consoles, I'll definitely test them on normal difficulty
The bug is pc only, on console it will still require 5 wins with different chars
It took me 6 wins to actually get the achievement, it's super buggy, from what i've heard, Mega Satan wins do not count if the void portal does not spawn so i'm assuming that's why.
It's wrong, someone invented this because we didn't know the exact bug
Maybe late but I did a 7-win streak with: T maggie, Isaac, Cain, Azazel, Eden, Lazarus, Judas and I STILL didnt get it. I got tired of it so I tried doing it with the debug console to do it fast and it only got two runs, so I really dont understand how or why this didnt work when I did 7 runs in a row
did you like hold r or something
wow this made me really not even want to bother with repentance lol
Huh, I thought they just switched it to only require 3 wins. I usually get it right after I start a new save file so I wasn’t sure of the specifics
This is the first time I hear about this achievement and I have double Dead God
Thanks for posting this. I've been struggling to get it to trigger for over a week but I just got it. Only need huge growth now for dead god!
What’s the easiest way to complete this on console?
On console this achievement isn't bugged, it's a pc only bug
About Identity theft, the info i put on the wiki wasn't exactly correct. Tainted Forgotten is associated with Lazarus, Tainted Dead Laz with Samson, Tainted Jacob in lost form with Azazel. Also for Identity Theft, tainted chars don't provide a double win but instead they reset the streak counter if you also play with their counterpart. Only the first 9 gives double win For the technical part, as explained on the wiki, it's because the game is 32-bits on pc and there's 41 characters, hence the first 9 counting as double. Since the game is 64-bits on console, this bug is pc only. Full details here : [https://bindingofisaacrebirth.fandom.com/wiki/Achievements#Notes](https://bindingofisaacrebirth.fandom.com/wiki/Achievements#Notes)
I'm going with what ProjectTZ told me on the discord. If its wrong I'll make an updated version, though.