Most of the obvious have already been said, but Teraflare in FFXIV hasn't. Fitting the actual encounter version is just as good as the End of an Era cinematic.
Unfortunately, all the videos of just it are wipes.
https://www.youtube.com/watch?v=DFboldco3ho&ab_channel=AgentJGaming
You fight a mini-Bahamut inside Bahamut as the actual Bahamut is huge. To put it in perspective, you can see one of his wings in the first turn of the raid, and you fight on one of his claws in another turn of the raid. And the entire raid storyline is a race to shut down the systems repairing Bahamut before his body is fully healed.
And then T12 is also a runner up as you get a CG cutscene after beating it that explains what happened in the white space between Louisouix fading away and the "A Realm Reborn" part of the CG trailer that debuted when ARR launched showing how Bahamut came to be in this state.