There was a bad ending plot where during the whole 'Ren gets into Shido's palace and tries to help Akechi thing goes south. Instead of having his interview later in the day, he had it earlier, and noticed Akechi heading to the diet much earlier (before he found out about his plan being useless) and Akechi ends up killing him when Ren puts two and two together after Goro saves him from a shadow.

Goro then leaves Ren's body on Shido's ship and is just...fucked up by the whole thing, doesn't find out his plan with Shido is useless but suddenly he has no one to text that night for a fun debate. All his plans with Ren later that week are practically cancelled, has a bit of a meltdown about it but tries to justify it to himself about how he's come too far to go back now. He comes up with a whole plan about how he'll feign ignorance when Ren is declared missing, being the first person to bring up the whole thing with Sojiro and plans next morning to go to Leblanc so that he's not suspicious....

Except when he goes....Ren is there...making coffee.

Goro would freeze of course when they make eye contact and Ren just smiles. Ren just asks him if he wants his usual and Sojiro notices Goro is acting weird but Goro just says its stress. Goro of course is freaking out on the inside, the thing in front of him talks like Ren, sounds like Ren, has all of his mannerisms but it can't possibly be Ren because Ren is dead because he killed him.

But this 'Ren' doesn't act suspicious beyond occasionally smiling at Goro, which no one else finds suspicious. Goro immediately checks for Ren's body in Shido's ship and when he gets there there's nothing. He starts to question his own sanity, wondering if he killed a cognition, but then why would Shido have a cognition of Ren on his ship? It's maddening especially since he can tell that Ren is toying with him, that smile that he knows more than he says but plays it off when asked, and manages to put on the most convincing acting performance of life and Goro feels even more gaslit. He doesn't know what to think anymore.

He tries asking his online friends if anything has been weird with NotRed, they don't notice anything suspicious. It's just him and that damn smile.

That's when Goro plots to kill him again in the real world this time where they would have no choice but to be a body. Is the one who brings forth his name to Shido as the leader of the Phantom Thieves just to have the excuse because having to pretend nothing is wrong is driving him mad. Because if Ren knows all of his secrets, if Ren is pretending, if Ren is NOT Ren, then that thing could undo everything he's worked for and is blaspheming his friend's memory to do it.

Not that Goro thinks he deserves to consider himself Rens friend anymore.

Anyways it was supposed to be another one of the ATOTT Yaldaboth bad endings I had in mind. But I couldn't decide on an ending and it was frankly too depressing to me but if you're wondering if it's supposed to be Ren, then yes it was, and he definitely wants payback and not just from Goro.