Finale — undertale

Flowey's DEFENSE dropped to 0!
As the six human SOULs start to rebel.

Finale is the 80th song in the Undertale Soundtrack. It plays during the phase of Photoshop Flowey's battle when the human SOULs help the protagonist defeat him.

This theme consists of a brass-orchestral (and breakcore) mix of Your Best Friend along with it being in minor key.

Trivia

The song in the game files is split into three different files, titled "mus_f_finale_1_l," "mus_f_finale_2," and "mus_f_finale_3," the last of which is continually looped throughout the rest of the battle.
There is an unused shorter version of the first part named "mus_f_finale_1."
In the game, "mus_f_noise" plays when "mus_f_finale_1_l" transitions into "mus_f_finale_2." This doesn't appear in the OST version.
From 0:40 to 0:58 of "mus_f_finale_2", Memory can be heard in the background as a bell-like instrument. (Orchestral Essentials Glockenspiel)^[1]
Like Your Best Nightmare, this song uses amen break samples.
The OST version and game files version are both different renders of finale, you can hear the differences by phase cancelling both the OST version and the game files version.