Who was more of a threat to Tamriel, Harkon and his vampires, or Miraak with his daedric powers? My bet's on Miraak.

Yep totally going with Mirak. Like the vamp guy was nasty but he didn't seem like that big of a threat (and I suppose i am just so over the whole vampire vs werewolf cliche that I didn't care for this DlC a whole lot and only bought it for the snow elves). Mirak, however, sided with the dragons and the bringing of the end times so I felt his threat played more into the story of Skyrim and thus also made him a more fearsome enemy.

"Freedom from the minor inconvenience of the sun" vs. "i'm mad at you! For some reason.". That's a tough one

Miraak because he's dragonborn.

Harkon is just a vampire.

Harkon, because of the lack of foresight.

Miraak may have been able to actually do something about the Thalmor.

Miraak, hands down.

Harkon would be his own undoing. His wish would have the world turn on vampires. Miraak has much more force behind him.

Being that Harkon wanted to

I'd say Harkon.

Harkon would have just ended up causing the eradication of Vampires. And someone would have found a magical means to fix the effect. Probably the Thalmor with Dawn magic experiments again.

Miraak probably could have ended up taking over Skyrim and other parts of Tamriel, so I'll go with him for sure. Especially since he had Hermaeus Mora backing. Or he would, if you died. He wanted to escape and was disloyal, yes, but HM had a firm grasp on him anyway.

Miraak's only doing the will of Hermaeus Mora (even if he might not think so). So the real question is Harkon vs Hermaeus Mora. I don't believe HM has any intentions that threaten Tamriel, so I'd vote Harkon.

Of course, if HM did want to be nasty to Tamriel, he's going to be a major problem, just like Dagon was in Oblivion.

Miraak, because he's Dragonborn and he's teamed with Herma Mora.

Harkon, simply because it's easier to carry out. You know how long it would take for Miraak to get those little shrines built in every province?

The Volkihar plot is more like "shoot an arrow into the sky and boom, goodbye Sun".

And he would have gotten away with it too if it weren't for that meddling Dragonborn.

Pretty much. Both were about as threatening as an angry toddler wanting attention. "Mwahahaha! I'm evil! Look at me!" was pretty much what they were going for.

Except that Miraak isn't mad at anyone. Being a Daedric Lord's slave svcks and he wants out.

Oh? So sending assassins after me is just his way of saying hello? Silly me.

And that led to his own downfall because good luck escaping the grasp of Daedric Prince that has his tentacles so far up your ass. As threatening as a rebellious teenager then.

This is why a Daedric Prince makes for more of a threat. Like Jyggalag.

"Miraak harbored fantasies of rebellion against me."

I like the way Hermaeus Mora laughs while saying that.

When eliminating a potential threat, you don't necessarily hate the poor fellow.

At the end of Dragonborn, Hermaeus Mora killed Miraak. You may have weakened him, but I doubt Mora needed you to, he probably just wanted some entertainment before he killed Miraak. Given that, I think Mora was planning on killing Miraak from the beginning so he was never really a threat. Though, Mora probably wouldn't have killed Miraak until the Last Dragonborn was under his sway, so our character did have to intervene, but Mora would probably not let Miraak go one way or another. Harkon on the other hand wasn't under anyone's control. If the player didn't stop him he would have eclipsed the Sun. Also, Harkon has vampires attack innocents, Miraak only sends cultists after you.

And Miraak enslaved lot's of people and turned them into brainwashed cultists

His influence was contained to Solstheim, though. Who needs it . Neloth would have freed them eventually...maybe...

True. Well, make it "Hello. I'm sending these losers after you'll so you know to come kill me before my plan is complete" then

I would definitely say Miraak. But I would rather put the Arch Curate Vyrthur against both of them. I found him to be far more of a threat than both of them

I mean come on! He's the mighty badass who blew the roof off his own house before you fight him!

Btw, I can just see Alduin saying "Why am I not considered a bigger threat? Huh?"

You know, I was expecting a more "So you are dragonborn like I am? Why not join me and we could rule the world all together just me and you." Would have made for a good devious plan too. But that is a very VERY strong plot twist to the lore for sure