I just had my longest and hardest fight in skyrim so far.

With Kvenel The Tongue
Spent 2 or so hrs trying to kill him, after repeated fail attempts.
But finally got him, feel so accomplished.

Krosis. Did not like his nuke fireballs. Used plenty of potions and took maybe 40 minutes for me to finally kill him.

playing on expert... undead mages are hardest in my opinion... so less dmg, my atronach do nearly nothing cuz mage run away
companion always die fast -.-

spend 1hr for the one in the cave
and 1hr for the one near a dragon stone on top of a mountain

yes: krosis was the name of the second one

ya some of there bosses get real hard on expert and master. i was getting one shot dead if i got near.

The first dragon i had to fight by myself. It lasted a good 20 minutes and took about 3 retries.

A Frostbite Spider in Cidhna Mine

Trying fighting a boss that teleports and splits into 3 forms and disarms you every 30seconds are so. Oh an your weapon goes flying and bouncing around the room and lands in the water so you zoom in an look at the floor like someone who lost a contact while you get nuked by him and his 2 adds and you cant find your weapon so you pull out extra crap you looted an start beating the boss with it.. an its on Master Difficulty. It svcked. LOL.

A female conjurer in a fort i visited. she shot ice spikes at me with rediculous accuracy from across the room as i was flinging endless arrows at her. when i got close to try to attack her she summoned a huge ice astronach that nealy one hit me. after sprinting around avoiding it and her ice spikes, i searched for something in my inventory that may give me an edge on her. i came across my ancestral wrath power, took cover and used it. i burst into flames as i used whirlwind sprint to get close fast. i pulled out my blade and started slicing away at her and lighting her up with flames. finally with an epic finishing move she was dead and her ice buddy disapeared, and i got to plunder the chest she was guarding for an awesome staff and a bunch of jewels and and a spell tome. this battle was by far the most intense fight.

Minor spoiler, but wait until you meet him the second time. There's like 5 of him, and his shout is the full FUS ROH DAH. I kept getting flung around the room and peppered with arrows. At that point, I was like, "[censored] that, Boss, meet console commands"

A female conjurer in a fort i visited. she shot ice spikes at me with rediculous accuracy from across the room as i was flinging endless arrows at her. when i got close to try to attack her she summoned a huge ice astronach that nealy one hit me. after sprinting around avoiding it and her ice spikes, i searched for something in my inventory that may give me an edge on her. i came across my ancestral wrath power, took cover and used it. i burst into flames as i used whirlwind sprint to get close fast. i pulled out my blade and started slicing away at her and lighting her up with flames. finally with an epic finishing move she was dead and her ice buddy disapeared, and i got to plunder the chest she was guarding for an awesome staff and a bunch of jewels and and a spell tome. this battle was by far the most intense fight.

Volsung.

While fighting him, I really hated my life. I raged. And then I raged some more. And then I pounded a beer. And then I raged some more. And you get the picture.

Took me one hour to beat him from the time he popped out of his coffin until the moment he fell before my claws, reloads included, beer-fetching not included.

Kvenel was not that bad for me. I had a worse time with other undead in that place (the undead lords, or whatever they are? the ones that disarm you with shouting? Yeah, those guys are much more difficult for me).

Krosis was tough.

That unfortunately placed frost troll on 7000 steps was annoying, but I managed to take him down at level 4 using every trick and potion I had.

Recently, the toughest fight I've had was the Deadra inside Azura's star. Those guys just spam the fireballs, which just flattened me in seconds. For some reason, they still did massive damage even though I'm around 75% fire resistant. It got me to wondering if enchantment resistances actually do stack.

I find it amusing and somewhat aggravating that a damn frost troll is harder to kill than a dragon

Krosis on lvl 7, hehe, got him after 300-ish iron arrows and glitching myself between some rocks so he couldnt hit me. Eventually the a.i. freaked out which made my PC freeze every 5 seconds...

But my toughest -fair- fight was against some random bandit leader with way too much armor and a ridiculous attack speed. God, that dude hit fast, almost four times my attack speed. Had to reload 10 times and drink almost 10 litres of health and stamina potions during the battle with him and 4 henchmen

I spent a solid 45 minutes fighting a dragon with Lydia. I was dodging the fire by taking cover behind rocks, it was epic. I acted as bait, drawing the dragon to me while Lydia shot it constantly. After about 30 minutes we brought it down, but it could still fight. Another 10 minutes later, it was weak. Lydia was down. It was just me and the dragon. I was planning on playing it safe, hiding behind a rock and shooting spells at it..but then the theme tune started to play..and it made me feel heroic as hell! So I drew my huge Steel Warhammer, stood over the edge of the wall and looked down at the beast. It opened it's mouth to shoot fire at me, but just before it could I Shouted "Fus ro!" at it. It'd stunned it, but only for a few seconds..so I jumped down and hammered it's head. Damn, it felt epic..

Hardest: My first Spriggan.

Longest: One Blood Dragon and a fort full of Forsworns (the dragon aggroed them, what can I say?)

One of the dragons...don't remember which one. But I was watching my health bar and his, and they both only had a sliver left. I got him, and then a spider ran up and killed me! ARGH!

So far nothing too long. I am hoping for Umbra because the Orc in Oblivion was rock solid.

In the end I lured her out of her dungeon and got her to chase me all the way to the nearest major town without laying a finger on me. Once there I let the guards see her attack me and then got up somewhere high so she couldn't get me and the whole guard house poured out to fight her.

THAT was an epic battle, it wasn't 2 hours or anything but it lasted quite a while.

Eventually the guards killed her and I looted the Umbra sword off her.

That was in my top ten gaming memories of all time.

I have say, so far, Krosis.

That blasted grenade-launcher/mini-nuke fireball staff and his ridiculous resistance to magic... Probably didn't help that I was level six at the time...

Still, he's dead, I've got his mask, his staff and the power off the dragon wall he was guarding.

Take THAT you pompous, overpowered zombie jerk!

http://www.skyrimnexus.com/imageshare/image.php?id=1072

Anyway, I was playing on Master Difficulty, as I'm sure many of you do, when I was around level 5 or 6, and had just discovered Dawnstar. I was in the middle of a battle with one dragon, backed up by some of the town people, when another dragon turned up, and landed ontop of one of the houses! I was just like "Ahh sh**"

Needless to say, confronted with 2 dragons, me and the entire town were destroyed. I reloaded a quicksave, which was during the fight with the first dragon, and when the second one turned up again, I ran....

I haven't been back to Dawnstar yet, I dread to think what has happened to them all!

who ever the enemy holding staff of magnus is, and i still havent killed him. he one shots me with lighting, while his summon one shots my atronach. A few more levels and its time to go back in and finish him off. difficulty=master. if anyone has taken this guy down without getting one shotted can u pls tell me what level you are.

Auuuugh Krosis! His fireball spamming wouldn't have been so bad if he wasn't also really good at kiting me around.

Mine had to be the entire city guard at Markarth. I had like 30 of them chasing me - I jumped off the top of a waterfall to land in the water and so I could swim away. I felt like the Fugitive with Harrison Ford! Now it seems I can't go back there,....

Draugr deathlord with a Ebony bow can kill a level 15 character in steel plate armour upgraded to flawless in 3 shots, knocked him down a pit leaving him with next to nothing hp only to find another deathlord bellow thankfully no bow. battles with deathlords don't last long they cleave through your health.
Any of those masked draugr dragon priests fought two so far both evil.

Krosis. I'm just so glad I killed the dragon before I walked up to the wall.

edit: actually, a fight with a dwemer steam centurion would be the hardest if I didn't use the cheap route of going in a place where he couldn't come and kill him with arrows..