Rinon's vid and end of expansion thinking got me thinking on favorite fights. Haven't done Ultimates, and started Savage in Eden's Promise (E9-12) and did all of Pandaemonium Savage on content. And have done every Extreme, but only Endwalker and late Shadowbringers stuff on content.
I definitely prove the theory of "your first fights being your favorites" as I think the top of my list is E9S and P12S P2. Cloud of Darkness in E9S just had a lot of fun mechanics to execute, and I think the Tiles part is still my favorite Savage mechanic I've learned so far. It looks cool to execute, requires a lot of teamwork, and is absolutely hilarious on voice chat when someone messes up or doesn't move when they need to. And of course the fight being when I learned somewhat how to raid heal felt good.
Oracle of Darkness is such a clean fast fight. The relativity mechanics are great, and each of the Apocalypse mechs feel nice and dangerous. Lots of great sound effects and all timer boss voice lines. And once you learned the fight to felt pretty good and not stressful which I liked for a final fight in comparison to all the final fights in Pandaemonium. P4, 8 and 12 all have moments that always felt on the edge of disaster no matter how many times I'd done it. Which is maybe good difficulty and fight design, but I dunno they always just felt too close to the edge of even if I know exactly what to do it was much too easy to explode.
Rounding out the top 3 for me is probably Seat of Sacrifice EX because that fight just has it all and executes so well on the concept of fighting a Warrior of Light.