Listing just some is always such a daunting task, there are so many amazing battle themes I've heard over the years that narrowing them down becomes harder and harder
I'll just stick to URL links so the thread doesn't become cursed like another recent thread did.

I expect most of the themes I'll list in this post will be (final) boss themes, which in a way makes sense because that's probably where you want your battle music to shine the most. That said, maybe if I feel like it I'll make another post later with just regular battle music

Ar nosurge - Ra Ciel Reincarnation: https://www.youtube.com/watch?v=o8tiJ8oHfao
Ar Tonelico 2 - EXEC_over.METHOD_SUBLIMATION/.~omness chs ciel sos infel: https://youtu.be/G8YOoQ-Py88
Ar Tonelico - EXEC_HARMONIUS/. : https://youtu.be/28ySSYp8fnQ
Ar Tonelico 2 - METHOD_REPLEKIA/. : https://youtu.be/4UwIP-gsHHY
Yakuza 0 - Pledge of Demon: https://youtu.be/K7R_xQUiZvg
Yakuza 6 - Destiny: https://youtu.be/_ynAxA770tk
Octopath Traveler - The One They Call the Witch: https://youtu.be/HxprIHuxG_s (See also Daughter of the Dark God, a slightly different version)
Xenoblade Chronicles X - Uncontrollable: https://youtu.be/xOeb7StJlRc
Nioh 2 - Tokichiro II: https://youtu.be/-1VaHo4dnng
Atelier Ayesha - MARIA: https://youtu.be/EVcc16o0SaY
Caligula Effect Overdose - Peter Pan Syndrome (boss version): https://youtu.be/NiCi_O41a-0
Ao no Kiseki Evolution - The Azure Arbitrator: https://youtu.be/E4-eqVc_G0U (I can never decide which version of this I like more, so since I posted the other in a different thread, this thread gets the Evo version)
Trails in the Syk SC Evolution - The Merciless Savior: https://youtu.be/vJO4oJ0Uce4 (same as above really)
Trails of Cold Steel 4 - Majestic Roar: https://youtu.be/mY3YczOUGcM
Trails of Cold Steel 4 - To the Future: https://youtu.be/F_8Sh9zL59s

I'll leave it at 15 for now, don't want to go overboard