Cumulonimbus

Yes one of my favorite contrapunctive cues! Also highly contrapunctive (yet not by definition a fugue):

What classical music is he into? Back, Mozart, Chopin, Tchaikovsky, ...? Piano, chamber music, orchestral music, ...? I think The Book Thief is quite classical too.

So not favorite score, not favorite cue, just the melody! I think we can safely say that John Williams is one of the most creative minds of the 20th century (debatably topped by for instance Rachmaninoff) in composing melodies and definitely is the most creative of the 21st century up until now. For me, it would be Fawkes the phoenix.

Yes excellent. Imo this one can certainly be considered one of the most complex in terms of orchestration. Considering the title, I think the OP asks about the complexity of the orchestration. To me that seems to be about which instrument plays what and when, and how many instruments play at the same time etc, the colouring of the music. We can add this as well: Mine cart chase from ToD.

Battle of Yavin climax. Incredible.

Does Where dreams are born counts? Or do you consider it to be the same as answering For Always? Anyway, I vote Where dreams are born.

Yes, either TFA, TESB or Jurassic Park.

You mention seamlessly. I find that the March of the Resistance comes in too sudden, not a big fan of that transition. The rest is, as you mention, indeed dazzlingly good.

All time favorite will be E.T. and then of course Adventures on Earth: in my opinion the best cue JW ever wrote, feels like a last movement of a brilliant symphony. Personal favorite: Far and Away, the Land Race.

Can we take a moment here to just appreciate the sheer brilliance of this cue. All the themes which are woven together, even a new theme for the falcon, snowy's theme, Tintin's theme. The change in metrum when Haddock falls through some laundry, the flute when the falcon flies through the building, the climatic version of Tintin's theme at the end. I cannot recall a cue by another film score composer that has this level of complexity!

'I don't have plans to slow down,' he says. 'I think slowing down happens to us anyway, whether we plan to or not. So why plan it?' Very nice quote, if everyone would think this way...

The Lost World is unavailable for me, anyone else has this problem as well?

Wow this one is great, could have been much longer for me.

This melody in the clarinet, you never hear it again in the soundtrack, but it is so beautiful. Only a few notes before it transforms into one of the main themes.

This. Though I find TFA to have a little bit more variation, Tintin is more similar throughout the score. Which can be seen as both a good and a bad thing I guess. TFA has a larger emotional spectrum imo.