Alright, it's time to toss in your opinions.
Of all the games you've ever played, who was the hardest boss you ever encountered? It doesn't have to be "the last boss" or anything. If there's a part in the game where they force you to fight this really hard boss for the level at which you face him, feel free to talk about that too. Also, feel free to discuss your experiences with the epic battle against your toughest boss!
I'll start. This is gonna be long. It's such a memorable fight, after all.
For me, so far, the hardest boss I'd ever fought was the Iselia Queen in Star Ocean Second Story for the PSX. Iselia Queen is the bonus dungeon boss, which you don't have to fight, but probably should because it's so much fun. She had 3.2 million HP in a game where damage was capped at 9999 per hit. I was at max level for all my characters when I fought her (finishing the bonus dungeon almost ensures max level), and had the best equipment possible (the whole point of the bonus dungeon is to get the best equipment). Even so, the Iselia Queen has various annoying attacks. Some attacks can kill in one hit, some are long-ranged and chase you around the entire screen, some poison, paralyze and petrify you all at the same time, that is, if you actually survive the damage. This meant that you had to sacrifice one of your equipment slots for anti-paralysis and anti-petrify at least (you can ignore poison for a bit, if you have a lot of antidotes).
First time I tried to fight her, I didn't really know what to expect. The walkthroughs I read only said it'll be tough, and that it'll take a long time to finally bring her down. Some even went so far as to rant about how annoyingly hard the battle is, but since I'd never experienced the battle, I couldn't understand much of it so I decided to just hop in with Rena as a frontline fighter (player-controleld), and Dias because of his high damage attacks, and Celine as the caster and Noel as the healer. As soon as the fight started, she immediately killed in one long-ranged attack Noel and Celine. So that was a shock. Soon after, even after repeatedly reviving Noel, I went down in about 4 or 5 minutes, especially since I was running low on healing items and resurrection items.
So I loaded back up and went to town to buy more stuff, and make more healing stuff using the alchemy system. I stocked up significantly, and decided to manually control the healing myself with Rena, since her melee attacks didn't require any skill spamming, so the MP was being wasted by not using them for healing and resurrecting. I brought Rena, Claude, Dias and Opera Vectra this time. I lasted quite a longer time, but Rena got stunned randomly and died in the next hit. So I was controlling Claude without a healer, trying to use items to resurrect Rena. While doing so, Claude dies. Rena is back up, but healing herself. I switch back to controlling Rena. Dias is taking a lot of damage, and as a strategic rule, always heal the alive first before reviving the dead. While trying to do that, Iselia Queen randomly used a long-ranged attack on Opera, who was firing from a distance. Somehow I forgot to give her anti-paralysis and anti-petrification, so she's stuck there for a while. I paused the game and tried to figure out how to deal with the situation.
Rena was at 70% health, and one hit could probably kill her. Dias had about 20% HP left, but he also had the armor that had defense that went up as the HP went lower, so he would probably last a bit longer. Claude was dead, and Opera was paralyzed and petrified. I decided to use an item to cure Opera, and use a mass heal so that both Rena and Dias would benefit, if only a little bit.
That was my mistake, though. I forgot that as Dias' hp went up, his defense also went down (due to the armor). So when I healed him a little, his defense went down just enough for him to take enough damage to get him killed. The item timer was still ticking, but Opera was cured, though damaged due to the poison. I paused again, seeing that my plan backfired. Without Dias or Claude to absorb the damage, Rena was probably going to die next, and Opera would be petrified and paralyzed if attacked, making item-use to try to resurrect Rena a lot harder. I went ahead anyway, and that's exactly what happened. Rena died in about 4 hits (trying to resurrect Dias), and Opera got petrified and paralyzed.
I tried to learn from my mistakes, and fought her a third time. This time I made sure they were all equipped properly. I brought the same team out, and to help out, I gave Rena more defense. Everything was going well, and I made sure that Rena was only attacking from behind to minimize the chances of getting stunned/killed, healing the others as necessary. Claude and Opera would die quite often, but nothing I couldn't handle. A simple resurrect spell or item was all that was needed to fix it. This continued for about 25 minutes. By that time, I realized that Rena was low on MP, and I was running out of items. I was wondering how much damage I'd done already. If this kept up, I would run out of items and die for sure.
It's now 30 minutes after I started the battle. With much difficulty, I think she was about to die. But I was already out of MP items, so I had to rely on the remaining 8 resurrection items.
About 35 minutes after the start of the battle, we're finally out of items. Claude dies, and soon after, Opera does too. I was running for my life as Rena, as the Iselia Queen was chasing me, and Dias was chasing her. Eventually I got hit and stunned by a long-ranged attack. This gave Dias time to catch up and draw her attention from me, which saved my life. A healing item got me back up, but Dias was taking a lot of damage. I didn't want to heal him "a little" again and make him die like before, so I busted out the big healing items, the stuff that heals for 100%. Soon after running out of them, I wondered if the battle was about to end finally. I continued attacking from behind, which I probably shouldn't have done. Later, she turned to me, attacked and killed me in about 5 hits. Now Dias was on his own. I took control and just pounded with regular attacks, because I had no MP and MP items left. Thanks to the armor, Dias was holding out quite well, but he can't last forever. He had about 200 HP left. Suddenly, the screen goes into slow motion. The Iselia Queen is dead!
The epic battle drew to a close, finally after almost 40 minutes of hard fighting, including lots of stressful micromanagement.
They really did a good job of making a difficult bonus dungeon boss. It's one of the highlights of the game, for sure.