For me, it has to be Guzma's boss theme and Vs. Ultra Beasts. Guzmas' is a fresh kind of theme and it's really cool to listen to. Vs. the Ultra Beasts reminded me so much of Super Paper Mario's weird and, often otherworldy or ethereal-sounding music. And of course, SPM is one of my favourite games of all time.
Personally, I liked the Lusamine themes the best. They had this feel of wickedness and evil to them, a feel no other villain theme has had before.
My vote is on gladion's theme, it just makes me want to battle AND get up and dance! *dances like old guy from the 50s*
I love Red and Blue's theme, I feel like it fits them so well. But the Champion Title Defense theme had me jumping in my chair. It surprised me so much.
I love the Tapus' battle theme. Pokémon has always been really good at making atmospheric battle themes but this one really sounds like you're fighting a force of nature https://www.youtube.com/watch?v=_u-rBhq-auk
The E4 theme this time around is one of my absolute favorites. I'm going to add it to my phone soon so I can listen to it during my commute. <3 Also really fond of the Champion battle theme because whoaa, Pokémon theme song and the player's theme song! A lot of people mentioned Guzma's theme.. and here I am, barely even remembering what it sounded like. ; ; ha haa...
All of Team Skull's songs. They sounded really serious but with Team Skull's stupidity it just makes it really funny. Also Hau's Theme is very energetic matching his personality.
Team Skull had some mildly intimidating themes, but if it weren't for their silliness... I mean, the hand arm waving thing was just ridiculous But I'm a more serious note, I enjoyed Red and Blue's battle theme, as well as the E4 (I get that some people put it down, but I like it, except for that one part where it kinda sounds like a warbled mess...). Both of Lusamine's battles themes are awesome, as are the Guardian Dieties. UBs have a pretty cool one. But I don't understand Gladion's theme. It doesn't really make sense to me...
I have to go with the Elite Four theme. Plus, hidden inside the music is a tune of a certain summoning theme.
The two best pieces of music in the games were Battle! (Tapu) and The Battle at the Summit! The first one I enjoyed because of the tribal underlay they have in the background, which feels absolutely authentic to Alola's Hawaiian roots! The second was simply amazing to listen to in general. The first piece absolutely smacks you in the face with nostalgia, and the rest makes it a truly amazing piece to listen to. I'm not sure if any of the other Champion themes can top this one! (Except maybe Cynthia's)
My favorite would have to be the team skull music. It's honestly the first time I ever enjoyed evil team music and I mean come on, the clash between the awesome music and these chuckle heads is just commical. They gave absolute clowns the hardest music in the game. That st least says something about them.
VS the Elite Four was one of my favorites in the game. Lusamine's second theme is also very goof. I love how intense it is! It fit the feeling of facing opponents you had no idea how tough they were... and they were surprisingly good using Z moves and all.
my favorite is definitely all of Lusamine's themes and Lillie's themes. Lusamines songs had some sort of..eerie and scary feel to them. and Lillies had a cute, upbeat theme to them if that makes sense.