the entirety of the soundtrack is absolutely phenomenal, probably the best soundtrack of any game ever IMO, every single song is damn great and fitting to what is going on; because of that i feel the songs are even better when heard during the actual game, which everyone should play. that being said, some of my favourites:
this is the track one is going to hear most playing the game & it captures the tone of the game PERFECTLY while never managing to be boring/stale
a boss fight theme this time, just a gorgeous track
this is one of the final tracks of the game(and one of the first ones actually), it's played during an incredibly stressful and long sequence of stuff going on; the energy again, matches up
so well with what is going on while still being fantastic as a standalone
honorable mentions go to
Copied City and
End of the Unkown. you'll notice End of the Unkown is completely different to basically every other track from the game; it's basically a one of thing and that's what makes it even better in my mind(and also heavily aids to the point i was making about every song perfectly fitting what's going on)
there's tons and tons of other amazing songs in the OST, such as Wretched Weaponry, Memories of Dust, Grandma(Destruction) and so many more, i wholly recommend both the game and the OST.