Tirek, the only male and the only one without wings, and the one who even has a backstory explaining his actions to a degree, or at least partially how he got there.
The one that doesn’t fit in is Tirek.
Chryssalis had 3 attempts at taking over Equestria, the closest she got was the third attempt. First attempt, she nearly took Canterlot and captured
Celestia, Cadance and the mane 6, but she didn’t seem to have any plan for what to do about the rest of equestria. I doubt the rest of Equestria, the royal guard or Luna where about to surrender to changeling rule just because Chryssie has one city.
In her second attempt, Chryssie managed to kidnap all the princesses and mane 6, but again, she didn’t seem to have any plan for how to actually take over and run Equestria afterward.
The third attempt was likewise a fuckup.
Cozy may have come close to destroying all magic in Equestria, she did not however have any way to take over the country or make anyone else obey her.
Tirek did steal all the magic in Equestria, the only reason he didn’t proceed to burn it all to the ground for shit and giggles, is Twiley pulling a new source of magic out of her plothole at the end.
The difference is that he didn’t try to take over Equestria and thus didn’t need to figure out how to actually take it over and run it after winning.
@StinkHorse
Because he, instead, wanted to go out and capture/destroy Twilight. He was the smartest of the villains, I wouldn’t say he’s the least irredeemable.
Of course one is different. Tirek actually had some theoretically redeeming qualities (like unresolved insecurities driving his motivations) that the other two lacked, and was also the least overtly sadistic in handling their prisoners
