The Witcher 3: Wild Hunt

I'll second what Banjo said. I can't speak on the Unseen Elder path but both achievements can be had if you save prior to speaking with the girl with the flint in the Syanna option. Finish the game from there once taking the ribbon and once not taking it. Way faster than starting from the beginning of Night of Long Fangs.

The achievement glitched for me as well. But I did a hard-reset of my console and replayed from the checkpoint where Geralt goes to confront Syanna. Achievement popped this time round during the ceremony.

I voted negative only because you could have avoided quite a lot of the spoilers you included. I realize some were unavoidable, but I don't need to know at least half of the story spoilers you wrote to get both the achievements

This and the other top solution for the other ending are very unclear. At the start of the solution is should say plainly which choices to make for which, not compare the two endings. It took some serious reading before I could figure out which choices to make for which achievement. And figuring out that the other quest doesn’t give an achievement (well may Kling of the Klink? See, it’s very unclear.)

To those who had this achievement glitched and not able to unlock it after using the methods in the above comments.

A last resort I found to unlock it was to go to setting of xbox > system > console info > reset console > reset and keep my games and apps

After reseting the xbox and going through the triggering scene, I finally unlocked the achievement. Yet, there is a risk that your save files may be lost. Like me, the system deleted all of my save files except one right before talking to Syanna. That’s why you might want to try this method at the very last moment.

Think there's a glitch in this achievement... Spoilers ahead...
I finished the game with the "happy ending" (Anna and Syanna both live), got decorated with the Order of Vitis Vinifera (got proof in my inventory), and no achievement pop ...

I went down the "Beyond Hill and Dale" mission branch...
So, from "Night of Long Fangs" I went the "Follow Damien’s Unit" path... During "Beyond Hill and Dale" I got the magic ribbon for Syanna, and was nice and understanding to her throughout (ending in the love scene)... Once I got once out of the Fablesphere, and Regis and Syanna began arguing I told them both to behave... Due to the ribbon, during "Tesham Mutna" Syanna lived, and I fought Detlaff... Starting "Pomp and Strange Circumstance" I went along with Regis to investigate the fifth victim further, asked all questions I could with everyone, read the letter from the beggers, and then confronted Syanna in the tower... I told the guard at the tower nothing of what I knew, just that I had to see her and he let me in... I was nice and understanding with Syanna again (so option 3 first up, then "forgive her", then "she was a child"), then went onto Guard Captain Damien... Talking to him, I said nothing of what I know of the fifth victim, and went onto the ceremony... There I went the second option, then picked "Free to do as I choose", next "Syanna’s crimes were horrible, but she had cause to feel pain", and finally "you were both children"... Anna and Syanna made up and I went onto see Regis... After all that and the final final happy ending, still no achievement...

Eventually got it to pop though by going back through all the above (I had made a save just before leaving Fablesphere, leaving all the the ribbon collection outstanding, to go back and follow the thread to get the Kling of the Clink achievement), following the exact path with one change... When I saw guard captain Damien, I told him of the fifth victim... All he did was express concern and indicated he'll increase Anna's protection, and it was onto the ceremony...

I'm unsure how that one line seems to affect the achievement... Maybe it's just me, as no-one seems to have brought it up yet after some googling... But on the chance anyone else has issue though after following the same thread, that could be why...

Perhaps something to make note of in the achievement guide?

Yeah, Calex dEUS is correct. I'll detail my experience a bit further if anyone is interested in specifics.

I chose the option to go to Damien during "Night of the Long Fangs" with a back-up save before that choice just in case (I ultimately did not need this back-up save). I then did everything in the Fablesphere EXCEPT talk to the girl with the flint, then went to her location, and created another back-up save (this is the important part - it ensures you do the least amount of work for both endings).

I went through the rest of the story last night without talking to her & got the King of the Clink achievement.

I reloaded the Fablesphere save this afternoon, talked to the girl with the flint, obtained Syanna's ribbon, and went through the rest of the story & got the Last Action Hero achievement. Confirming both are possible when choosing to go to Damien during "Night of the Long Fangs".

I am unsure of whether both endings are possible if you choose to go to Orianna instead, but it sounds like you'll end up in the Fablesphere either way, and that the deciding factor is ultimately whether you get the ribbon from the girl with the flint or not.

I think it's worth noting that both endings were great & it's worth the effort, in my opinion.

Bit late, but for others who may get the problem that this achievement doesn't pop:

I'm quite sure the choice of dialogue before and during the ceremony doesn't matter in terms of whether it pops or not - it's only a matter of actually getting the order. Normally, the achievement will pop exactly when Anna Henrietta pins it on your chest. If it doesn't, it may be the usual random Xbox Achievement delay, or it may simply not pop.

If it doesn't pop, as RavenWraithe says, it's enough to go back to the checkpoint or a save game right before you (can) confront Syanna. May even be enough to keep a save game before the ceremony itself (i.e., don't talk to Syanna, or tell the guard that you'll go to Damien yourself rather than immediately after meeting Syanna, and then save before talking to Damien) - since it isn't a "complicated" achievement - it should be (and likely is) implemented as "simply" a check that you get to a specific point in the ceremony.

I went through the talk with Syanna and the ceremony itself 3 times (with all the same choices) before it popped - then it did so immediately. Note that only my 3rd attempt was after a shutdown of the Xbox - the second was right after seeing the achivement didn't pop. So may only require two attempts, not a "random" number. Or it may be something that's still in memory until you shut down that interferes with the achievement.

ETA: After playing some of the other endings, figured out that not talking to Syanna may not trigger the achievement.