Braniac Maniac - Plants vs. Zombies | Super Smash Bros. Ultimate

Remix of "Missile Maestro" (Colored Pencils boss) and "Elastic Entertainer" (Rubber Band boss) from "Paper Mario: The Origami King"

Tony Dickinson: Guitars, Keyboards, Production, Mixing, Mastering
Connor Engstrom: Guitars
Max Noel: Bass

Satan's Office Supplies

Missile Maestro/Elastic Entertainer (Paper Mario; The Origami King) Epic Metal Remix

DKCR OST - 93 - Tiki Tong Terror

Metal Mario (Wonder Effect) - Super Mario Bros. Wonder OST

Three Shadow Sirens Battle - Paper Mario: The Thousand-Year Door (Switch)

[Vinesauce] Joel - Reaction To 7 GRAND DAD

There's a download

I noticed that some gameplays of the game had the boss battle theme playing clearly well, so I compiled and mixed clips where only the music plays.

Mid-Boss - Mario + Rabbids Kingdom Battle - (Pre-Release version)

Kirby Star Allies Full Soundtrack

Void Termina (Phase 4 - Soul) - Kirby Star Allies Music

Super Mario RPG: Fight Against an Armed Boss Remix (Luigi's Mansion Soundfont)

Nightmare  - Kirby Star Allies

Tee Lopes - Labyrinth Zone Re - Imagined

[Vinesauce] Joel - Reaction To 7 GRAND DAD

Cybervibes