Heres my order from strongest to weakest (judging from the only two films I've seen)
Nagumo (final form): Complete power house. Could reshape a landscape with a seemingly limitless supply of energy beams from his penises, absorbed victims and his middle eye.
Ma-O: Immensely destructive. Like Nagumo, he too could reshape a landscape, only this time by manipulating weather.
Amano Jyaku: This guy could take on a direct hit from Nagumos plasma sperm and it just made him mad. Plus, his regeneration is astounding.
Suikakuju: Has some decent physical and elemental manipulation moves about him, though he is quite frail.
Takkeaki: Strong, fast and aggressive with spiked tentacles, much more of a brawler than Nagumo (2nd form) was.
Ozaki: With the exception of Jyaku, no one could touch this guy. Too fast and far too brimming with power.
Nagumo 2nd form: Pretty much an immobile, completely reactive creature with decent physical strength and the ability to manipulate its own bodily fluids.
Kohoki; Fast and vicious with razor sharp wings, though possessing little in way of defence.
Megumi: A flying chick with super strength.
Nikki: A vicious bruiser with sharp teeth. Little more than a slavering animal.
Myuni Hausen: Though impervious to energy attacks due to a magic shield, he is extremely vulnerable to physical attacks.
If you're trying to play hard to get, play harder! I like it rough!
I would have to say Overfiend because Overfiend is like God and the only being who can beat him is himself. The Evil King is Overfiend's dark half, so in essence, that would be his match. But the host body is usually too weak, so the Evil King gets delayed for a while before it returns in a new form. Beyond that, it's like I said. Overfiend can't be beat. In the case with other characters apart from Overfiend, it's clearly Amano. He is a Jujin whose powers as a warrior are unmatched. His powers as a mystic are not quite mastered, but he more than makes up for his lack of experience with youthful enthusiam. Plus, his family history has a lot to do with the amount of power he has. He is part Majin, as one of his ancient ancestors was a demon from Makai, making him quite stronger than the usual Jujin. But let's not forget Megumi. She is special, and the Overfiend knew this, that is why he had sex with her to transform her into his agent of destruction. Not unlike Akemi, she can be filled with the Overfiend's seed and not be destroyed. But Overfiend had to use a receptacle(demon bones) to fornicate with her in order to ensure that she could survive the process of them combining their energies. He knew that his power alone couldn't defeat the elemental that Faust/Munchaussen had summoned(which is the physical manifestation of ultimate hatred) so he used magic to seduce Megumi and every time he made her orgasm, her body was being prepared for his member. It made her transform into her true Jujin form and when they both climaxed, she became an avatar for him. Their combined might destroyed the elemental but she remained under his control. That alone makes her the second most powerful female character, Akemi Ito being the first as she is the mother of the true Overfiend, which makes her pure energy. Other than that, everyone else is second string.
Your list is accurate to an extent, but it's extremely over simplified. But that's ok. There's no need to be sooo freakin' accurate anyway. I mean, It's not like anybody except maybe us is going to really pay attention to any power statistics. Lol! We may just the biggest Urotsukidoji fans ever if we start cataloguing super powers like the way that Marvel Comics does with their Official Handbook. You know, that would be f---in' awesome if they ever did that. A book like the Official Handbook Of The Marvel Universe but with Legend Of The Overfiend. And with the same art from the manga and the anime, along with the two varying histories from each. Oh, man! Ok, ok, I must relax.
I could see the Urotsukidoji New Saga as the Ultimate Marvel Universe aspect. Since just like Ultimate, New Saga is a spin off/update of the original "mainstream universe". Buju would be considered the Amano type of character for the Makemonos. He is to the Makemonos what Amano is to the Jujinkai. With his sword, that would make him slightly stronger that Amano, but only in the sense that the weapon is stronger. If Amano got his hands on the sword, Buju would be in just as much trouble as Amano would be in if he fought Buju with the sword. The sword is what makes the difference. Beyond that, they're pretty equal in my eyes. As for Kyo-O, the power of chaos is equal to the power of order, the only difference is that chaos can only destroy, while order can only create and recreate. Their very natures are their only limitations. Apart from that they are two halves of the same coin.
Ma-O didn't hurt the Overfiend. All he did was delay him. Ma-O was nothing but a minor inconvenience who was easily dealt with. The only character who could possibly hurt the Chojin was that dragon in part 3 who was created by Faust/Munchausen/Munni Hausen. Faust claimed that it was the "physical manifestation of ultimate hatred" and whatever form of attack that was used by Amano in order to try and stop it failed because it only made it stronger. That's why the Overfiend needed Megumi to unify and magnify their magical powers in order to destroy it with an immense energy blast. Overfiend knew that he was in trouble and he did what he had to do in order to ensure his survival.
Ma-O was nothing more than a great demon from Makai who had the power of the oceans at his command. He may have been hot s--t to practically every other character on account of his sheer size and strength, but as far as the Overfiend was concerned, he was small potatoes who was only summoned by Suikakujyu out of desperation. In the end, after all was said and done, Ma-O sucked.
The Overfiend was definitely hurt but he could never be killed by Ma-O. The Overfiend is like both God and the devil put together as one combined being. How in the hell could a "great demon of the oceans" actually "kill" its creator? Just because the Overfiend can be hurt doesn't neccessarily mean that any form of injury can do any kind of permanent damage. Even if the Overfiend was down, it was only a temporary setback. He always recovers and soundly trounces anyone who thinks that they can beat him.
He made an an example out of Ma-O, just like he made an example out of Takeaki Kidu mentally possessed by the Evil King, just like he made an example of that weird dragon thing in Urotsukidoji III and in the end, in part four, he was making an example out of everyone and everything on Earth(just as he did in the other two dimensions).
It got so bad, that Himi began to panic and reincarnated the universe in a last ditch effort to stop the premature destruction of the three worlds. She was only barely successful, as you can tell by the Urotsukidoji New Saga.
but thats just it,its the great story of the creator being killed by its creatION,frankenstein is the perfect example.Theres a reason Ma-o was called the GREAT demon,it killed many demons before it,and yes it had less chance against the overfiend but it had power and experience of battle.It wanted to be the next overfiend. Just like you say,the overfiend beats everything that comes against him,but thats how his enemies learn.Ma-o still had as good a chance as anything else
Ok, if you say so. Those factors aren't what the parameters of the story entail as far as how Toshio Maeda had invented the characters, but if that's your take on it, I won't argue with you. We'll just have to agree to disagree that's all.
IIRC, the one thing that was able to finally kill the Overfiend was the Kyo-O in the form of Himi.
At the end of Urotsukidoji IV: Inferno Road, when the Chojin gets down with Himi, she unleashes her power as the Kyo-O and destroys him and effectively resets the timeline.
I'm aware of the alternate ending to Inferno Road that was supposed to be the set up to Part V, but seeing as Part V was never finished and the one OVA of it that was produced is a bit of a mess, I think IV is the end point for the series, with V as a weird "What If" take on the original continuity and New Saga being its own entirely different thing altogether.
Although given the ending of Inferno Road implies the timeline being reset, it is possible that New Saga is a sort-of distant sequel to the original four films set in the new rebooted timeline.
New Saga did kind of suck, but a lot of it was due to the project being cut short and that it was supposed to be a complete retelling/reworking of the Overfiend saga before becoming the vague weird retelling of the first part of the first film that we got.