I like the idea of him apparently sinking deeper into insanity after each defeat

The Mega Man X Legacy Collection puts it best with the individual achievement names for defeating Sigma in each game.

X1 - “It’s Over”

X2 - “It’s Actually Over”

X3 - “It’s Over… Right?”

X4 - “It’s Definitely Over”

X5 - “Alright, It’s Over!”

X6 - “I’m Sure It’s Over This Time”

X7 - “It Has To Be Over Now”

X8 - “It’s Over, Once And For All”

Even Capcom knows how much they overused Sigma.

I liked that with every defeat he seemed even more corrupted, but yeah it gets tiring to see him try again and again and again with almost no change to the formula

To be fair, sigma seems to actually be worth megaman's time. No disrespect to wily but he's usually all talk until he's defeated then he turns into a coward. Sigma keeps that same cocky attitude

He's just a Sigma male, none of you guys would get it.

Sigma in X7 sounds like the gray fish from the SpongeBob episode who talks about “muscles on your muscles”.

Good video.  I did indeed laugh when Sigma fell out the window.  And had the loudest facepalm when you played the X7 cutscene like you always DOOOO

Sigma is mortal because he's a sigma male

How many times do we have to teach you this lesson old man?

With X8, it appeared they finally realized that while they could get away with Wily nearly always being behind something bad, however, it did not translate as well with Sigma. So Sigma technically perished for good in X8. Even if he still existed in virus form, he can do jack squat against the new generation of reploids and is completely useless against carbons when it comes to infections. If X9 ever was made, it's likely that Lumine controlling Axel's body would be one of the threats instead.

Sigma male rule 235: get your ass kicked 10 times and never learn anything

If you ask me, even if the series ended with X5 Sigma would have overstayed his welcome. X2 and X3 could have worked without Sigma.

Dr.Wily works because he is goofy and until he creates Zero, not that threatening at all. But Sigma? He is the commander of the Mavericks. That being said, the zombie Sigma thing in X6 could have worked if he was made an optional bonus boss, with the heroes going "Oh shet Gate wanted to revive Sigma"

At least Megaman X Command Mission showed us what a canon X story could look like without Sigma

He went from being a terrifying Villain to an over saturated generic Tyrannical overlord-type villain

I would argue Sigma's loss of menace isn't because of the number of losses, but rather how he is just shoehorned in to be the end villain, especially after X5.  Because when your master stroke is trying to ruin the planet for humanity while getting X and Zero to turn against each other, I feel like that's the pinnacle of threat that a fallen maverick hunter turned sentient computer virus can pose. Anything after that is just a step back and just makes Sigma look petty.

Sigma in every X game be like: Are you ready for round *insert game number here*? (hope you get the reference)

Sigma could work in Mega Man X if the series had more main villains for X to fight. Make MMX2 and 3 with new villains, then bring Sigma back for 4 and 5. That's how I would've done it.

You know honestly i always felt kind of bad for Sigma, He seems to fall into the category of a Tragic Villain since it really wasn't His fault that He went rogue/turned evil and became a Maverick, it was His first fight with Zero where He was severely injured and infected with the Maverick Virus that set the madness into motion through no fault of His own, honestly a part of me always wished He could've been cured and eventually became a Maverick Hunter again helping X and Zero against a new threat since He was never inherently bad to begin with, just a victim of circumstance, i personally liked the fact that He appears in every Megaman X game, accentuating the fact that Sigma has as many lives as Agent Smith from The Matrix Lol

All hail the Maverick Devil King (Irregular Maou), Sigma (Shiguma)! The strongest MegaMan villain among of all the MegaMan villains from all MegaMan series!

Nowadays he’s name means very different to Gen Alphas