I don't count giants as enemies because they do not attack on sight, spriggans are easy with a certain weapon, but frost trolls, those are a freaking pain for my light armored Bosmer, they regenerate way too fast, most of the time I have to use unrelenting force on them and make a run for it while they are stunned.

Hah, "steamrolled."

Bears, sabre cats, dwemer centurion guards, trolls, atronauchs, apprentice mages.

Oh yeah I've ran away from a lot of things. My daggers only shave their health and I'm like nooo...

Yes, that pun was intended.

I had a hard time taking out that frost troll on the way up the mountain to high hrothgar too, but he wasnt too hard to get past, for me the hardest enemy definitely has to be a blood dragon, i've only fought two and the first one I only managed to kill cause I had a load of the guards from the area distracting the dragon whilst I blasted him with my spells, other one completely destroyed me

Well, i was all alone up by the shrine of azura at around lvl 5. I hear a roar look up and see a dragon disappear behind the mountains. A few minutes later he pops out from behind the shrine and that was the hardest battle i've had so far. But it was SOOO satisfying when i finally beat it. I felt like an ACTUAL dragonborn instead of having a bunch of people help me.

[censored] me, I rather have 2 trolls and a giant than what i got just now ...
was following a quest (not gonna tell wich one ) and in the end, there were 2!! Hagraven and another tough dude.

luckily saved just before it. restarted it ...hmm ... 5-6 times, trying all different things. when it was finally going well for me, my companion, Lydia, died -.-
after restart 7 i finally got lucky with the use of potions, shouts and a good portion of luck

toughest so far

I think it was the Kronis (I forgot how to spell it.) I approached a word wall and had to beat a tough dragon, then when I went to unlock the word the Kronis popped up. It took my 25 potions, 50 arrows, and around 75 swings of my axe. Hard as hell. I learned all 3 words of the shout with 1 wall though, that was nice.

Trolls and Giants scare the holy guacamole out of me! They are just such power houses; not to mention that I'm only level 9.

Same for me...that bastard was insane

trolls in general are insane. I saw one thought it would be a walk in the park...I was wrong...2 shots and I was dead

Toughest would be the saber cat that would start chasing me on the way to Riften and kill me in like three hits. Since it was by a bridge and there wasn't space to sneak around, the only way I could survive was to use some scrolls of make it run away that I picked up somewhere.

But since I'm a thief and don't know anything about magic yet, there were some difficulties with that also. Instead of the "click and the magic happens" scrolls from before, I'm just waving my hands around, making a lot of pretty lights, but not making the cat go away. So it took a few deaths and reloads to get that to work properly, and when I did figure the "charge and release" thing out, the cat apparantly lost interest and didn't follow me across the bridge that time, so I had to waste the scroll.
Luckily, another one showed up on the next mountain path and I still had one of the scrolls left, so I had a chance to demonstrate my arcane mastery after all and then sprint like crazy out of there.

Giants. They hit me once or step on me and I'm dead.

I've got a trick for you guys against frost trolls. They follow you have & have stupid AI, so try and find a ledge from which you can snipe it from.

For example, if you are going up the 7000 steps and the Ice troll drops down to your right, bait it to follow you. Turn around & keep running, if you keep running there will soon be a small ledge (on your right), jump on it & flame it + time your attacks without getting 2 hitted.

I've killed Ice Trolls by finding a small ledge to snipe it from. It just stands there trying to swipe you.

I ran into something called a Wisp Mother? Anyone seen those yet? This is the only mob I absolutely had to run from. It spams you with some spell that drains your stamina to nothing, it also puts an effect on you as if you're over-encumbered. Oh and it does heavy damage. I couldn't escape it because duh! I had no stamina to sprint away and I couldn't get close enough to hit it because I'm not only slow as hell but it would be constantly backing up to keep room in-between me and itself. Only thing that saved me was the dragon shout that propels you forward (forget the name). I used it to propel myself off the cliff we were fighting on and into a lake. lol

God that was a mother of a fight.

Bandit boss for the first Companion quest. He skewered me instantly on that 2 hander 5 times in a row. Haven't even had any issue with my first dragon, or my first Draugr Overlord.

Some named Dragon Priest near a word wall in the middle of nowhere.

Damn he was unbeatable, until I saved my game, TGMd and Fus Ro Dahd him off a cliff.
The shout from that wall is a bloody sweet reward though.

After that Frost Trolls no doubt. Ran into 3 at the same time when scouting Labirinthian, jesus christ.

Elder dragons hate those killed me with one fire breath when i saw first time one of those

Hah for me it was the frost trol aswell. I have nbo idea who put that mob in the path to the second styoryline quest but that damn thing is imposible to kill as it regenrates all the time...I had to use my nord shout to make him run.

I owned the Frost Troll, but I had my in-game wife attacking it too with a bow so it wasn't as hard as it would have been fighting it solo. The HARDEST for me though is definately the Giant. Every encounter with one so far has sent me a couple hundred feet in the air. xD

Trolls and Whispmother (don't know if that's a singular mob or if there are more of them). I don't think I could take more than one Whispmother at a time.

Also, at a Word Wall, the first I found, after managing to kill the Dragon,

Frost dragons,trolls and Giants

Trolls, they are to slow to die and they regenerate!

Morokei on my pure mage. No contest. At all. I've killed plenty of giants and ice trolls and what-nots, they are easy.. Morokei took away 90% of my health and 50% of mana THROUGH a bloody ward with every single attack from range while my double casted lightning bolt, if I managed to even get one off without getting hit, did like 5% dmg to him :[

Tough but not smart, I was on horse back and led the saber cat into Riften where the guards killed it, I was not sure it was going to work because other creatures tend to back off when you get near the entrance of a settlement.