I have beaten the full game and chose the "Resist" option end game, watched the credits, and did not unlock the achievement. I'm also not getting an option to replay the last mission. I have also gotten every other story mode achievement except for this one, so I should have it unlocked? I'm so confused lol. Thanks in advance for any help.
Same here dude, unfortunately its affecting a lot of people on all platforms. Ubisoft is aware from videos ive watched with this bug. I chose walk away and sat through the credits twice with no luck to unlock it and it wont even let me play the game as it keeps showing credits every time i hit continue. So my thing is ill replay the game and choose the other ending this time hopefully the game is updated by then.
Thank you for reporting this to us.
Unfortunately it's not possible for us to manually unlock achievements for the Xbox, so if it didn't pop then unfortunately as the Support mentioned on Twitter replaying may be the only option.
I believe the option to replay the last mission is only there if you pick the opposite of what you chose.