Gaenor and it isn't even close for me.

Ugh I forgot about him yeah I didn't like him at all. Also the adoring fan.

Haha Glarthir, If i start a new character he's the first Bosmer i kill

It's because Gaenor was supposed to be an intentionally annoying and nigh unbeatable character. And while I regret meeting him in game, I'm sorta glad they added him in.
So you've guessed it, my choice is Gaenor by far. The horror, my god the horror...

Glarthir. It seems I’m tripping over him every time I walk into Skingrad.

All Male Bosmers are annoying, and deserve to die. Maglir, Adoring Fan, Gaenor, Glarthir, the arena guy, Thoronir. The list is endless. My all time hated person has to be the creepy-as-hell guard from Anvil with the scary-ass pig face. I scream whenever I suddenly see his face and he yells, "Stop! You've violated the law!'"

Glarthir, damn him.
I kill him on sight.

Maglir offends me.

Well, even though I highly dislike Glarthir, I will have to choose another because everyone chooses him.
I very much dislike is Modryn Oreyn.
At first, you meet him and he is in a pissy mood.. And it's clear he dislikes you. He never TRULY develops a friendship until he is exiled of the guild and you are his only hope. But, most of all, I hate him for one reason.
Walking. To. The. Ayleid. Ruin.
After you clear the first ruin looking for Blackheart you follow him for like 10 minutes to a ruin that you know where it is but he needs to WALK there. Damn.

The Adoring Fan.

Am I the first one to name this little bastard?

Even non-Bosmer NPC's think the Bosmer are annoying!

My most hated is definitely Owyn, though. Aside from the "I heard a rumor you're an idiot" line, none of his dialogue seemed funny. They were just insulting, and I (and my characters, mostly) have an intense dislike of him.

Yeah, he was pretty annoying. I tried to help him out when I was relatively new to Morrowind. The fact that he uses hand to hand and that I found him at such an early stage in the game was really frustrating.

Lord Gothren.
His stubborn refusal to talk with me at all meant all my usually peaceful characters always had to kill him.

Maglir.
He was so annoying, craven, cowardly and self serving that even my usually peaceful characters had a hard time deciding to use invisibility to avoid the final fight with him. And 8/10 times didnt.

Maglir. That [censored] midget....

The adoring fan...gaenor and every other annoying character i met could be killed, the adoring fan was annoying and had infinite respawns -.-

Else. Not that she was annoying, quite the opposite actually. I liked her and that made killing her when she went all "LORD DAGON!" kinda sad.

I found it odd that Else God-Hater, who hates all gods, worships Dagon. A clever deception.

Well first off.. Gaenor. [censored]. But, i am glad he was in the game - he was one of those benchmarks that worked as a test of skill.

Also from Tribunal, Thrud. He talks as though he is mentally challenged, and just talking to him pretty much starts up a quest. A quest that's not too easy, either. I would always accidentally take this quest before I was really capable, and end up getting Thrud killed, and then feel really bad for getting a mentally challenged person killed.

Also, http://www.uesp.net/wiki/Morrowind:Nels_Llendo_%28person%29. He was kind of a pushover but could cause problems for my level 1 characters straight out of seyda neen - which is usually when I encounter him.

By Thor, this!

Oh man...lemme see...

Gaenor definently top of the list...My god I was so pissed when he become the FIRST TIME I died. Yes, I went through all of Morrowind with out dying ONCE on Normal Diff (About Middle/twords the right on the Difficulty Bar lol). Tribunal had to inject this freak into my game...lol I must have slaughtered so many Vivec Guards...it wasn't even funny. But this [censored] here over clocks on the Roid Rage.
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Alot of NPCs who are SECRET memebrs of the Cult in Oblivion...I think one is named Kayn or Rayn or something like that, She hangs out at one of the taverns/inns where your Fence is. (An Orc, Wood Elf run the place)...I made great friends with her....but then got into a fight with some one and she Sports the Summoned Armor ish from the Cult of Mehrunes who tried to kill the Emperor.

I keep running into ALOT of them. I'll get into a Fight at a bar, and then all the sudden some one I liked as an NPC/Helped me find something when I talked tothem, or was just overall nice...BOOM! BIG SURPRISE...

I hate them because I LIKE them...but I have to KILL Them.
-Edit- Ranoline, a High Elf with a secret, is the cook here, although the inn doesn't have a kitchen.

http://www.uesp.net/wiki/Oblivion:The_Lonely_Suitor_Lodge
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Antoinetta Marie and Gogron gro-Bolmog. I liked them too...killing them svcked.

An Imperial Legion Captain. Right after pickpocketing. He's "essential" and it took me a few gameovers to figure it out.

Glarthir. Talked to him, didn't want to accept his crazy quest, and he goes and kills one of the Surilie Brothers.

The assassin that killed Uriel Septim. We were almost out of there too.

The individual I regret meeting was Uriel Septim. Why did he have to go through my cell. He almost got me killed too. True story.

Gaenor...

I hate you so..