Here's a list of the phase fours:

Pathetic

Game Over

Unpredictable

Rainferno

Until My Last Breath... (In the image the gradient is supposed to be a rainbow, but I'm not making an entire GIF just to do that.)

Uplifting Struggle (A normal fight for this phase is basically canon.)

Credits

Sprites by Zerjox and Red Teamworks (Edited by me)

Undertale: Last Breath by Zerjox

Undertale: Last Breath Inc. by Mr. Last Breath and Luna