Due to request of one of the admins, I shall indeed post a top 5 bosses.
One thing though.

HADES DOESN'T COUNT. He's obviously the best boss in the game and one of the greatest of all time, so what are the other bosses that don't count as a chapter that make your top five?

5. Aurum Generator

Yeah shoot me, I know, it's an Aurum boss that isn't Pyrrhon. Though easy with most weapons, The Aurum Generator is really fun to me. I mean, you fight it on grind rails. Not only that, Pyrrhon comes in and says my favorite line in the entire game.

"Ahahahaha! That is to say... oops, my bad.
"My bad!? That's all you have to say!?"
"No, I have one more message to import to you! I wish you luck! You're gonna need it.

4. Arlon the Serene

I love Arlon as not only a character, but as a boss. He made me use my favorite strategy:
SWING WILDLY WITH A CLUB UNTIL I HIT SOMETHING AND KILL IT YAY!

3. Chaos Kin

I am a huge fan of fast bosses. Examples are Phosphora and Arlon, but Chaos Kin really insues "Chaos" in its name with its battle. As I said before...
SWING WILDLY WITH A CLUB UNTIL I HIT SOMETHING AND KILL IT YAY!

2. Thanatos

All dem forms! ALL DEM SO FUN! ALL DEM ON ONE EPIC CHARACTER. THANATOS WAS BOSS. It really made you take on some strategy, and fighting him on 9.0 is really fun.

1. Aurum Pyrrhon

... how did you not expect this? Pyrrhon is my favorite character in the game, and when I learned he was a boss, I was like "YESSSSSSSS". Pyrrhon has a buttload of attacks and I find the battle super fun. The "receiving pain" and "owww" robotic voices when he takes damage was also funny.

OTHERWISE IT'S PYRRHON GODAMMIT.

2083280
Ha ha, it's funny because you made me an admin for some reason...

Anyway, in no particular order:

Hades' Heart from Lord of the Underworld
Apart from his whole berserk attack (the camera angle/controls are still one of the game's few definitive issues), it's fun to prowl around after this guy- like a cat stalking its prey. And depending on what weapon you're carrying, there are more than a few good ways to attack him. If you've got a staff, you can get ahead of him and snipe 'em. If you've got a club (that isn't the Magnus Club), you can shoot through the pillars to attack him (Slip Shot's always a good substitute). Or if you have a Palm (or anything else with good homing), you can arc your shots over the pillars.

Just God help you if you're using an Arm without a good speed modifier.

Medusa from Medusa's Final Battle
Although Medusa doesn't attack as rapidly and aggressively as I would've liked in this fight (until you pull away her façade), there's something about the scale, atmosphere, and overall tone of this fight that I find particularly enjoyable. That, and the second boss theme. It is epic.

Palutena/Chaos Kin from Palutena's Temple
Return of the epic second boss theme aside (it's a strangely underused track), all the tension that plays out during the land battle section finally comes to a head in this battle. Not only that, but tracking down and attacking the Chaos Kin while keeping an eye on Palutena is a boss concept that I like, and one that was implemented fairly well.

... Would you believe that the first time I played this boss fight, I just shot at Palutena without thinking?

Cragalanche from Viridi, Goddess of Nature
This battle can get pretty hectic at times, but a good kind of hectic. Dodging his attacks, getting around him and firing away really is one of the more exciting boss fights for me.

Also, you have no idea how awesome it was to finally 9.0 this guy using an Upperdash Arm with a good speed modifier. You have no idea how frusrating that chalenge was, but getting it was so worth it.

Amazon Pandora from Scorched Feathers
... If there's one reason that I'm not copy/pasting image files for these bosses, it's because I don't want anyone to get the idea that I'm adding Amazon Pandora here "because fanservice." Seriously, have you seen the screenshots and fanart of her?

But I digress, Amazon Pandora comes at you right from the start (even more so than fireball Pandora), sets all these traps around the Rewind Spring, and maintains some of that trickster persona she had before, making this a very fun boss fight. And it's also fun to watch her bitter grudge against Dark Pit play out. I usually like to bring the Pandora Claws to this fight, both as a touch of irony and to just run at her with their speed.

2087501 Actually, I dislike the Cragalanche boss fight a lot!
and I didn't have much trouble taking down Hades' Heart with the Magnus Club

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Cragalanche isn't too hard if you know when and where to dodge. In fact, if you dodge half of his attacks just right, you'll even end up right behind him. Just be careful with the second half of the fight; he gets much more aggressive when he's low on health.

Incidentally, while I like the Palutena fight in chapter 20, I absolutely hate Pseudo-Palutena in The Three Trials. That's when she really goes nuts with the projectiles, even summoning two or three options (think Gradius options) to shoot at you with.

2090515 And here I am responding 5 days later. I don't like almost anything in the Three Trials except its atmosphere. Dyntos wasn't too unreasonable of a character either. It's just that when I saw the Phoenix I just went "NOPE I HATE THIS CHAPTER"