The final Ultimate Mix of Battle Against A True Hero because why not end this dedication with a proper mashup? (And yes, I added one more.)
(I never intend on making money off of these, so support the original artists by supporting their channels)
Used themes:
@TheNobleDemon :    • Undertale: Battle Against a True Hero Arra...  
@Anjer :    • Undertale - Battle Against A True Hero (Me...  
@Cloudjumper :    • Battle Against a True Hero - Epic Orchestr...  
@RichaadEB :    • Undertale: Battle Against A True Hero - Me...  
@AnthonyLoReMusic :    • Undyne Theme : "Battle Against A True Hero...  
And most of all, thank you Toby Fox.
And to appease the viewers, here's the link to the thumbnail;
https://pin.it/2Dt7TNNM5