What was the last boss you've beaten?

...And how difficult (or not) was it? What game? Did you try more than once to beat the boss? =)

Sabrina in Pokemon Blue

It was the only battle so far where I was questioning if I was going to win.

My plan was to swords dance with Kingler and easily beat her entire team, but Kingler became confused after the swords dance and fainted. Then I tried Flareon, which probably saved this fight, her Pokemon had poor defenses so body slam worked well here. Flareon went down eventually, so I sent out Fearow which immediately went down to a critical hit. I tried Clefable, which put her down to Alakazam with half health. My last options were Venasaur, which couldn't take a hit, or Rhydon, which has no special. Rhydon barley survived the hit, so I won with earthquake.

Ba'al vi; Goldie, from Bravely Second. Easy as heck, even when it's at Level 99. Beating Ba'als up multiple times can be fun, though.

The Arcanist, Ninja, and Hunter asterisk holders all at once! I'm on my third time around reawakening the crystals in Bravely Default and decided to see if any of the sub-scenarios were changed up. It was definitely the hardest battle so far for me. Templar with the Red Mage BP skills allowed me to spam Rampart, which is the only reason I won.

Asav in Uncharted 4. He was a little tough to defeat because he requires dodging, but I managed to not be killed by him and I beat him.

The final boss in Kirby Planet Robobot. It was more challenging than the rest of the game, but not particularly difficult (as one might expect with Kirby).

If Pokemon counts, then it would be Gym Leader Erika from Yellow Version. I used Pidgeotto against Erika and it was not all that hard.

The Necromancer in Castlevania Circle of the Moon. It was actually a really hard fight.

Was just doing some speedrunning practice, so I beat Dr. Robotnik at the end of Sonic 2. Considering I know a lot of the ins and outs of the game, the final boss was one of the easiest parts of the game- it was everything else that had me worried, haha.

Cleared a few dungeon runs in Hearthstone today, if those count :P Latest would be Vustrasz.

Ammo Baron in Shantae: Friends to the End. He's only the fourth boss in the game but he's easier than he should be.

Hearthstones Darkness was no match for my jades

and charged devilsaur

The Doctor in Cave Story, I suppose.

Karasuman in Castlevania: Symphony of the Night

Pretty much a joke fight. I kept pinning him against the wall while hitting him, so he never even got an attack off.

MAJOR SPOILERS FOR KIRBY STAR ALLIES INBOUND

Black Dragon Kalameet from Dark Souls 1 (i only played it after playing DS3, Bloodborne and Demon Souls)

Final boss of Etrian Odyssey V. I kind of regretted choosing Basic difficulty for pretty much the entire game, none of the bosses were difficult and usually died before they even got a chance to attack.

but this guy was significantly more difficult than anything else the game could throw at you, I can't even imagine beating it on Advanced without a team made for the sole purpose of countering it.

I guess I'd say it was more difficult than the EO2U final boss just by the fact that I felt the need to retire to win, but it was a lot shorter since it didn't 100% follow a pattern and its difficulty wasn't in its length but how quickly it could become too overwhelming to deal with.

Basaran, the 9th Colossus in Shadow of the Colossus. This was like...having a dog jump up onto the table and shit all over the half-eaten meal you were really enjoying up to that point. I was actually enjoying this game - bad controls and all - until I had to fight this thing.

The AI was absolutely awful - he often decided to stop directly in front of a geyser and fire undodgeable homing lasers at me. Nothing I did would get him to move over it - if I moved too far away he'd just pass over it and chase me, and if I moved too close to him he'd try and squash me. When I finally DID manage to flip him over with it, there was nowhere to hold on to the top of his shell, so he was delighted to throw me off...at which point I'd have to lead him back to a geyser. Which he stopped a few feet away from again and refused to move.

This thing completely ruined the game for me. Not exactly difficult, but so unbelievably frustrating for how utterly random the AI was. It took me about thirty minutes - climbing up him four times in the end - to actually kill him. I did a little reading after the fact and he's generally considered the worst boss in the game because of his AI, so I'm glad that's behind me, but that was an experience I did not need. After the previous eight were so cleverly-designed and dare I say it, fun to fight...this was so badly designed it was like it was cut out of a completely different game.