I know this rule wasn't clearly stated in the video, but I am only counting Robot Masters that had a numerical code/serialization attached to them. That's why (SPOILERS, if you care that much), Zero, for example, was counted, but not King. That's why I leave some of those up to your interpretation. There really isn't a definitive template that makes a Robot Master in the Mega Man series, so we'd be here all day discussing potential Wily-made machines if I didn't give myself some restrictions. Hope that makes sense.

Sources:
~ Windii's Stuff:
-- Archive of their Mega Man Stuff: https://archive.org/details/windii-gi...
-- Twitter (until that site goes under):   / girlbossuran  
~ Everything Else from the MMKB at https://megaman.fandom.com and the original print edition of the "Mega Man Robot Master Field Guide"

Track Listing:
~ Tengu Man's Stage - Mega Man & Bass (SNES)
~ Cut Man's Stage - Mega Man
~ Metal Man's Stage - Mega Man 2
~ Stage Select - Mega Man 2
~ Shadow Man's Stage - Mega Man 3
~ Bright Man's Stage - Mega Man 4
~ Gravity Man's Stage - Mega Man 5
~ Junk Man's Stage - Mega Man 7
~ Galaxy Man's Stage - Mega Man 9
~ Get the Punk Out - Mega Man 10
~ Overdrive Scramble (Special Stage) - Mega Man 9
~ Dr. Wily Capsule - Mega Man 10

Games Shown (in no particular order):
~ Mega Man: Powered Up
~ Mega Man 2
~ Mega Man III (Rockman World 3)
~ Mega Man 4, 5, 6, 7, 8, 9, 10, & 11
~ Mega Man V (Rockman World 5)
~ Super Adventure Rockman
~ Mega Man & Bass
~ Mega Man & Bass: Challenger from the Future (Translations here: https://www.romhacking.net/games/2499/ )
~ Mega Man X4

How did it take me so long to make a video with even less production value than the last?