Alright, for this post, my first real post, I'm going to list a group of video game bosses that I had a lot of trouble with. In no particular order, really. Just general painfulness.
Warning: possible spoilers.
Sephiroth, from Final Fantasy Seven
Theme Song: One Winged Angel
Who is he?
You know who this is.
If you don't, possibly because you're new to the Internet, or other fanciful possibilities, Sephiroth was the protagonist of Final Fantasy VII, and (possibly) single-handedly introduced the image of the white-haired pretty boy into the mainstream gaming view. Plus he had an outrageously long sword, too. He wanted to become a god or something like that.
Now, Sephiroth was probably not much of a problem for a fair few people. He was challenging but not too hard, and was a cinch compared to the ludicrous difficulty associated with Emerald and Ruby Weapon (which I have not yet beaten).
Why did I find Sephiroth hard?
I was like, ten years old. I found random battles to be one of the most infuriating things ever, which resulted in gratuitous overuse of L2 and R2. As a result, I wasn't very strong by the endgame usually.
How did I beat him?
By growing the hell up.
Nyx, from Shin Megami Tensei: Persona 3
Theme Song: The Battle for Everyone's Souls
Who is she?
Nyx is the final boss from Persona 3. I won't go into detail about what, exactly, she's doing as said final boss. Needless to say, it's not nice (or is it?).
Why did I find Nyx hard? Because Nyx is from Persona 3, a game from a series of hard games, published by Atlus, who delight in the general suffering their hard games produce. Whilst Persona 3 is probably one of the more forgiving titles in the Shin Megami Tensei series (with the earlier ones being infamously painful), Nyx was still one of the hardest bosses in a game that could, depending on how you played it, take you out the back and beat you like a dog.
Nyx also operated on a desperately cruel attrition strategy: you had to defeat Nyx about twelve times, and the first eleven times could be considered Nyx 'warming up'. The battle took ages to complete, and a defeat resulted in one of the most sadistic tools in the JRPG arsenal: having to repeat cutscenes and insanely long battles.
How did I beat Nyx? By levelling to level goddamn 99, that's how. Even then, it wasn't particularly easy.
Darth Malak, from Star Wars: Knights of the Old Republic
Theme Song: Darth Malak's Theme Song
Darth Malak was the main antagonist and final boss of Knights of the Old Republic, and despite spending most of the game acting as a really pissy child who threw his toys around indiscriminately (and coming off as having a serious inferiority complex compared to the more restrained, cooler Darth Revan), he made for a highly climactic end.
Actually, now that I think about it, Malak used the same bitchy 'fight the same fight over and over' technique which Nyx used, except she was far more hardcore about it. If he was running low on health he'd drain some sealed prisoners' health, making this quite a long fight. After Malak, I expected quite a hard fight from KOTOR 2, and whilst it most definitely was a hard fight, Darth Traya was somewhat less of a climax than Malak's berserk rage.
How did I beat him? I actually don't remember. I think heavy, heavy healing was involved, which involved a light character. I had the idea of attempting to parallel-game a light and dark character at the same time. My dark one reached Malak first.
France, from Europa Universalis 2 and 3
Theme Song: Le Marseillaise
Okay, ultimately some confusion can be caused by this entry. For starters, it's hardly a 'boss' in general, for the game lacks a linear story, but I decided to include it because it's the one I almost always think of first. For the unitiated, Europa Universalis 2 (and its sequel, Europa Universalis 3) are strategy games, ranging from 1420 to 1820 in world history. The general premise is that you choose a nation during the time period and play it to glory.
EU, and the general 'EU engine' games, are famous for being fearfully incomprehensible to new players, who enter and see a dangerously confusing interface, filled with strange concepts and a lack of any real help as to how to play the game. (The original manual for Eu2 was in some areas, just plain wrong.)
Now, veteran players of EU2 and 3 can make the game do some seriously broken things, like taking geographically isolated African nations like Xhosa or Benin and conquering the world, but we aren't going to talk about them. We're going to talk about me, and why France scares the hell out of most players in the EU series.
In both games, France occupies highly wealthy provinces, has a lot of manpower, and is almost always on the cutting edge of technology. It proceeds to use this technology to beat the living crap out of all of its neighbours, sometimes simultaneously, gaining even more power. In Eu3, the AI actually gives them free money and soldiers. Fake difficulty? Totally, but nonetheless hard, especially playing as traditional French enemies England, or one of the small German states (of which there are approximately 99 billion). France also gets some excellent generals, including Napoleon, who is possibly an elementary force of nature by that point. (The AI sort of screws it up, but God help you if France is being played by a human player). I have seen games where France has, as an AI, conquered Europe, starting with Russia, and squeeding everyone between them. Improbable? Yes, but that doesn't stop France from proceeding to dominate the rest of the game. Don't underestimate France. They'll proceed to beat every hilarious French surrender joke out of you with a baton.
How did I beat France?
Luck probably plays a bit of it, as the random events system can break nations on a whim, possibly catering to some sadistic deity. However, the best way is to simply wipe them out early, typically as England, when they're still weak, divided, and Joan of Arc hasn't saved their asses. Of course, an England which has conquered France will immediately become a goddamn superpower, which is good news for you if you're England, and bad news for everyone else.
Otherwise, you'll typically spend a goodly amount of time skirting the 'France' issue, and hoping they'll pick on someone else. Admittedly, I don't end every game of EU2 and 3 by grinding France into the dust: I simply don't have the time or the ability.