Patek Phillippe has a complication not mentioned on this list that is one of the most complex complication ever built: the Calibre 89 [1] that can keep track of when Easter is (to a point).
Another contender is the Vacheron Constantin 57260 [2].
Here [3] is a good demonstration of how a perpetual calendar works.
Ah yes, the Hebrew calendar on the 57260 is sorta mind-bending to figure out. It's hard to imagine figuring that out by mere observation and tabulating records. Their more recent Berkley Grand Complication [1] took things a step further with a Chinese Perpetual Calendar, which is kinda hard to explain. The article linked does a better job than I would at walking through the system.
Another contender is the Vacheron Constantin 57260 [2].
Here [3] is a good demonstration of how a perpetual calendar works.
[1]: https://hausmann-co.com/en/the-patek-philippe-calibre-89-the...
[2]: https://www.prestigetime.com/blog/worlds-most-complicated-wa...
[3]: https://www.youtube.com/watch?v=YERho3Q4Abo