I just reread the Osaka arc, and I had a couple of thoughts. First (this is a brief one), right before Katou goes to attack the acid-backed monster that initially defeated the Sadists (Chapter 251, page 2, Gantz 251 page 02 | One Manga ), Anzu yells, "Let me tell you about how to clear!".
How to clear? To "clear", as the Osakans say, is to get 100 points. Evidently, there is some sort of trick or strategy the Osakan team uses...thoughts?
More importantly, though, I decided to analyze the Nuri forms, and I saw what may be a pattern:
Nuri starts out in his old man form.
He then transforms into a child, then a nude woman. Kyou then shoots him.
He transforms into his tall, laser-eyed form. Kyou shoots him again.
Nuri is left as just a head, then the head sprouts arms, then puts itself back together into a form that resembles the laser-eyed version, except minus the lasers. George and Kuwabara slice him apart.
The pieces of Nuri transform into four variations on the initial "old man Nuri" form, which then combine to make one "old man Nuri". It dodges George and Kuwabara's attacks, then George grabs it.
At this point, Nuri transforms into a giant mass of nude women. He envelops George and continues to increase in size. George tries to cut his way out but is unsuccessful. Nuri forms himself into a giant woman made up of hundreds of individual, nude women. He then spits out George's head.
Kuwabara attempts to flee but is enveloped by Nuri. He ejaculates in Nuri's mouth and falls to the ground. Katou then fights Nuri. When he uses the Y-gun, Nuri abandons the composite "giant woman" form and turns back into a mass of nude women. Katou is enveloped.
Nishi then hits the "mass of women Nuri" with the H-gun, leaving only the arm and Katou. Anzu gets Katou out of the arm and they jump away just as Nishi annhilates the arm with the H-gun, leaving only a pool of blood.
From the pool emerges "Behemoth Nuri", the one that has a skull for a face, antlers, and all that stuff. He goes on a rampage and is decapitated by Oka. He then transforms into a mass of demonic-looking flesh, looking rather like a composite of Osakan Yokai. Oka palm blasts him.
From one of the pieces of Nuri-flesh emerges a taller, more muscular version of the "old man Nuri" form. Nuri palm-blasts him again, and when the dust settles this Nuri is sitting on top of some discarded Nuri-flesh. He and Oka fight, and he eventually shapeshifts to resemble Oka (though still in the "old man Nuri"-esque form). Then the milkshake incident occurs and Nuri is slashed up.
From the remains of that Nuri form arises the sphere of marble thingies that fly out and attack the Gantzers.
After the marble incident, Nuri is now somewhere in between the "child" form he initially transformed into and the nude woman form that Kyou shot. Oka's slash is still visible. Kaze beats the shit out of him and punches his head apart.
Upon losing his head, Nuri transforms into multiple male forms, similar to his "feminine hell" form. The Tokyo team blasts him apart.
Nuri then reforms in his most recent form, the demonic, skull-faced creature. He is then blown apart yet again.
Now, what's the pattern? Keep in mind, this is rather rough, but here's what I'm seeing:
Nuri starts out each "stage" in an "old man Nuri" form or variation thereof (the initial form, the form that destroyed Oka's supersuit). He then turns into a child/nude woman form (the initial transformation, the form that Kaze beat the shit out of), then an "odd" form specialized to take out his opponents (the laser-eyed form, which was meant to seek out his hidden attackers, and then the marble form, which allowed him to strike all of his opponents at once), then a "multiple bodies" form (the feminine hell form, the form that Katou and the Tokyo team fought). After that, he turns into a "demonic" form-the Behemoth and the form the killed Oka.
Then the cycle starts again.
In other words, we are at the conclusion of the second "cycle" of Nuri forms. The first cycle concluded when Oka killed the Behemoth, the second concluded when the demonic form was blown up.
What's next? Another cycle? God, I hope not.