Topic: Hardest bosses you've ever faced

Paper Mario TYD: Cortez
Galaxy: Bowser Jr.
Star Fox Adventures: Galdon
Super Mario RPG: the toads who turn into a boss
A Link to the Past: the sorceress who sends you into Dark World

EDIT: not sharks, toads

You thought they were hard? Have you fought the rangers yet?

A really hard boss that comes to mind is Sigma from Mega Man X.

I'm actually stuck on that boss.

Recently: Squizzard daredevil run (Super Mario Galaxy 2)
Ever: Bowser X (M&L Bowser's Inside Story)

Copy Megaman from Mega Man 1. Insane boss is insane.

Probably the final boss from Demon's Crest.

Also, did you really think that boss was hard, StarFox? Wait till you get to some of the upcoming bosses in the game, such as Valentina, Culex, and a few more.

Ozma - Final Fantasy IX
Angra Mainyu - Final Fantasy X-2 (ugh, this thing is a beast)
Culex - Super Mario RPG
Final Boss - Actraiser
Sephiroth - Kingdom Hearts
The Principal - LIT (ugh, the timing had to be perfect to beat him)
Otoshigo/Takeaki Misawa/Mother - Siren 2
Pyramid Head duo - Silent Hill 2 (hard difficulty, takes forever!)
Malus, The 16th Colossus - Shadow of the Colossus
Kefka - Final Fantasy VI

Bouldergeist's Daredevil Run from the first Mario Galaxy. Took me over 30 tries to beat him.

Super Ghouls N Ghosts on GBA/snes aaaaaaaaaaaaaaaarrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrgggggggggggggggghhhhhhhhhhhhhhh

Still have nightmares about it, im glad i did it but wont do it again for a while.

I probably needed twice as many tries. Then I had a, "What a moron I am, just pound the ground, you idiot," epiphany. Took maybe three tries after that.

Super Princess peach - the final, final boss, Bowser!... it was
nearly impossible to beat!
Eternal Darkness - augustine, final boss
Metal Gear Solid: the twin snakes - SNIPER WOLF!!!
Puyo Pop: fever - carbunicle
Hatsune miku: project diva - Dear Cocoa girls... instant fail...
Sonic Heroes - That Metal Sonic monster thingy (final boss), The problem I had was with the bad controls, not the boss itself...
Residents Evil 4 - Jack Krauser, I hate those dang "think fast" cutscenes!!

Anything in I Wanna Be the Guy.

Just to mention a few:

Ace Attorney Investigations: Miles Edgeworth ~ Final boss (not mentioning the name, obviously)
Banjo-Tooie ~ Weldar
Detana!! Twinbee ~ Final boss (can't find the name)
Final Fantasy Tactics A2: Grimoire of the Rift ~ Neukhia
Gotcha Force ~ Galactic Emperor
Luigi's Mansion ~ King Boo
Mega Man 10 ~ Block Devil
Super Mario Land ~ Final boss (can't find the name)
Super Metroid ~ Phantoon (I'll probably face some harder bosses later in the game)
Wario Land 4 ~ Catbat (Super Hard Mode/No items)

The following contains minor spoilers for Actraiser (SNES/VC).

The final boss gauntlet on Actraiser.

Never have I felt so hopeless.

For anyone who's unfamiliar, the boss gauntlet is every major boss you've fought throughout the game (the ones you defeat to purify the land of monsters - not the ones that allow you to settle in the land in the first place.), but harder, faster and (obviously) all at once - no heals (you get a limited amout of lives).

And then you have to fight the final boss and his two forms as well!

I'll probably think of more...

Can't really think of any. Probably something from an RPG though.

@edhe you mean the one i already mentioned?

And the ones that precede him, yes.

The Demi-Fiend in SMT: Digital Devil Saga comes to mind.

@edhe well, i kinda always counted the final boss as the entire thing, since you kinda have to do it all in one swoop...

that 'boss' was hard because the case was so boring, though. it wasn't much of a challenge except to keep your eyes open, lol.

also, the boss of SML is Tatanga. :3