I was first thinking of the most insulting boss in any game would be Glados. How he..she........well it kept making fun of you while you were fighting it. Saying you were adopted and how nobody showed up for your party, etc.

As for disappointingly easy, the only one I can think of at the moment is Metroid Prime. After fighting Metroid Prime in what I like to call "crab form" the "ectoplasm form" is just way to boring and easy. I was thinking the first time I played it "I have beaten this boss before. It just looked different".

The final boss in Dragon Age was ridiculously easy. I had trouble with Ogres and stuff, dying up to 20 times in each battle, but when I came to the final boss it went down quickly on my first try without any strategy whatsoever.

FF XII Vosler, I loved the game for its vast and free world, but Vosler just not menacing enough.

The last boss in Tales of Symphonia: Dawn of the New World, after you get defeated by the male and female bosses.

Yeah me neither. The fight against the 2 Scarabs on Legendary is unbelievable hard though.

FFXII

I didn't really do anything the entire fight... the game played itself... 

Ikaruga's last boss. not.

I played through Donkey Kong Country for the first time last week.  The last boss in that is ridiculous - I didn't even lose a life.  In fact, as tricky as that game can be in places, pretty much every boss can be beaten on your first or second attempt.  Very good game though, but the bosses are lame.

fable2.

The Saboteur >_>