I think for a branching / multiple endings game, the first route will always be the most special. Because at that point you'll be going in blind, to some extent. You may understand the vibe of the beginning of the game, and can extrapolate on the tone of the endings, but you'll never know for sure until you complete the route. You're forced to prepare yourself for the tonal shift that may or may not happen. And from that uncertainty comes a better payoff, in my mind.
For that reason I'll nominate my first ending of Grisaia no Kajitsu, Sachi.
I think this is my favorite so far of the lists you've posted. ~5 per category, roughly ordered by "noob-friendliness" is a good way to go. Particularly the inclusion of "Gameplay" as its own category is helpful to separate out games with elements beyond the usual read + make choices. Super information dense, but my eyes just passed over most of the symbols the first time so it's apparently easy to ignore the extra information if you're not looking for it. Besides not having read most of the works here, there's not much to comment on the game choices because they're largely the same in all these lists, so it's mostly the presentation of this version that I prefer.