What's the hardest boss battle you've ever done?

[The name master]

Self explanatory.

Mine is:

The final boss of sonic advance in the final zone.

Still beat it though! In your face, Eggman!

Actually the boss in that snowy zone place where you're under water. I keep drowning! I haven't defeated this boss yet! Why are sonic bosses so hard?

[Sizacu]

Hum... a number of bosses come to mind in Etrian Odyssey lol. If I had to narrow them down to two, I'd say The Forbidden One and Dragon both from EO4. The other bosses I fought in EO2 and 3 I had strategies for courtesy the internet...

[Milsap]

Nemesis in Resident Evil 3.

He never stops.

[Captain Jigglypuff]

The optional Agrabah boss in Kingdom Hearts 1 comes to mind. It took me over an hour to kill that thing. The Phantom was also difficult due to the Instant Death curse it places on each of your team members and I was annoyed that you're forced to have Peter Pan in your party to do the boss battle. I've always hated him, even in his own movie as a kid.

Other difficult bosses I've fought are Primal Dialga in Mystery Dungeon, Cynthia in Platinum on my first run through, Wham Bam Jewel in Hero to Helper in Kirby Super Star Ultra, Galacta Knight from Kirby Super Star Ultra True Arena, that robot worm thing in Shantae and the Pirate's Curse, and Ganon in LOZ Oracle games after defeating Twin Rova when I have no more Magic Medicine to replenish health after all my hearts are gone.

[lets all go out for some frosty chocolate milkshakes]

green hill zone boss in sonic 1

[Lord Raven]

Hmm, this is a tough one since I've played against many bosses.

SH1's boss took long as hell to beat down, but he wasn't hard as long as I stayed on top of my healing.

FF13 had some bosses that were tough the first time around but easy once you understood the battle system completely.  FFX has Yunalesca/Seymour Flux.

Castlevania had some pain in the ass bosses especially in the original games and Circle of the Moon/Order of Ecclesia.

Man I need to start playing video games again lol

[The name master]

Rudy the clown is the easiest final boss ever!

[Captain Jigglypuff]

Rudy the clown is the easiest final boss ever!

No. That honor would go to Kirby Super Star (Ultra) The Arena's Waddle Dee. It literally just stays in one spot letting you massacre it.

[The name master]

God, that boss from super Mario superstar saga was hard! The one that looks like jelly. I could never beat it. Hopefully that's different a few years later.

[Meowstic Royalty]

Primal Dialga from PMD2, HANDS DOWN. I had explorers of darkness, which should actually be EASIER since I get Violent Seeds, but oH MY GOD HE'S SO OVERPOWERED

[SirBlaziken]

Either Primal Dialga (even with vile seeds aplenty it took me ages to win. Dig is your best friend against it) or Metal Sonic in Sonic Heroes.

Xemnas in Kingdom Hearts 2 took only one try but I spent half the time healing and the other half running for my life. xD