Comment by Magic Marmalade:
Something and nothing.
This is an odd movie, which now I see why it has all the mixed reviews.
The reason being, essentially, that what with all the day-glo / neon / fluorescence going on, and the premise, of a a load of assassins on the titular bullet train, you go into this expecting something along the lines of a whacky, coked up, high octane John Wick style movie, but it's actually more dialogue driven... for the first hour at least.
..."Witty" banter and lightly comedic dialogue, only punctuated by the odd smidge of "action".
This presents itself, and indeed, tries to be a kind of ultra-neon, modernist Guy Ritchie / Lock Stock etc. affair, set against a Keyser Söze (ripped off!) style unseen devil mythology, where someone is pulling the strings in the background.
These plot devices are pretty clunky and contrived, and the whole movie is basically absurd, whacky, and cartoonish... perhaps trying a little too hard to be cool, and too clever for it's own good (and too clever for it's own ability).
So if you expect an adrenalin rush straight out of the gate, you will be disappointed on that score, and see all the visual aspects as mere window dressing to cover up that fact.
(Half a dozen gratuitous cameos don't rescue it either, and don't really add anything, seeing as they have precisely no bearing on the plot whatsoever - just twenty second jobs for acting chums!)
That said, if you don't mind it not being what you thought it was, it is quite fun, goofy nonsense, albeit a wasted opportunity, I feel... a bit like those Shane Black movies I've seen recently: Nice Guys and Kiss Kiss, Bang Bang.