Morrowind: Dagoth Ur
Oblivion: Jyggalag
Skyrim: Lord Harkon
the first two were no contest but in Skyrim Alduin and Miraak sucked as villains because Alduin had nothing to offer other than being the boss to defeated after a long dungeon crawl. Miraak on the other hand was the greatest disappointment in the Dragonborn DLC because i expected more lore on what it is to being a dragonborn rather just being a puppet for Hermaeus Mora. I mean WTF?!! Even his death was scripted! Couldn't he tell the player everything before his demise, which he surely knew was going to happen anyway?
PC Dragonborn: "Can't you at least tell me about being what we are and why we came into being?"
Miraak: "Well, look at the time. Mora wants to consume me utterly. Good luck asking him."
PC Dragonborn: "WTF?!! Well, back to slaying more dragons and taking their souls."
Miraak fight felt a bit more epic for me, on my first character I'd gotten to the Dragon Aspect wall before starting the Gardener of Men. After Mr Spoilerface died I read the book and went straight to the end. Still, they could've done a lot more with that fight rather than 'hit him until he becomes invincible and heals, rinse and repeat'
That's true. When you first see him it's pretty cool though, as well as when he steals you dragon souls all the time - finally get to kill him feels pretty good.
I think they should've built up a bit more mystery with him controlling randoms on the island though, by far the coolest moment of the DLC for me was doing that sidequest to distribute Sujamma in the tavern in Raven Rock, when suddenly everyone gets up, starts chanting and walks to the Earth Stone.
I guess they didn't really stick out for me because I did them on a character that was level 20+, and the Redoran guy glitched up for me and the conversation option wasn't there!
The thing with these people is that they were 'just people' - I was only including the more unique bossfights