Sasori (more often than not, though Deidara has a chance)
Kakuzu
Itachi
6 Paths
I feel that the 6 Paths are pretty much perfect for taking on phasing-only Tobi. They have perfect timing to strike when he attacks, it'll be very difficult for him to attack them. With Deva specifically, whenever he grabs Deva can repulse.
I considered that...but then I remembered that he has Izanagi that lasts 5 minutes. For five minutes, he can't be touched. Tobi is fast and skilled enough to warp them away in 5 minutes.
I think Deidara would beat Sasori personally. He knows about Sasori's weakness so he could plant mini explosives to find their way onto him while avoiding the other puppets at a distance.
Sasori's got an advantage in versatility. He has enough tricks up his sleeve that even being partners Deidara doesn't necessarily know what he's going to face.
Pain vs Tobi is the only one that is debateable in my opinion. I don't personally see Tobi having the offensive output to beat the paths, at least from what we've seen so far.
puppets don't protect you from c4 or the village buster that Deidara dropped on sunagakure. Once the outter shell has been broken, it really is to exploitable.
You're assuming they have a power never before displayed? Tell me you see the flaw in this.
No, but iron instead of silica, and it seem to be able to produce pretty large amounts, and it might be the amount it made there wasn't it's limit, it's not like Sasori taxed himself.
The Iron Sand also only has to reduce the blast long enough for Sasori's armored shell to survive, and considering it's major toughness, that's not too hard.
It's hardly the pinnacle. Having different puppets with different abilities is his schtick. He can pull out what puppet he needs for the situation.
If he took down Sakura, he'd have a new super-strength puppet.
He has many puppets made from other ninja he killed with an unknown large number of chakra abilities. We don't know the specific nature of those ability, but we very much do know he has an arsenal of human puppets with chakra.
Yet it never displayed anything close to being able to stop what Deidara dropped on the village. It got rocked by Sakuras punches and his shell got one shot by her punches. Seriously, stop.
Do you not see whats wrong with your argument? You're assuming things that didn't happen on panel or the anime. Why? This is the flimsiest argument I've ever seen. It amounts to "He probably can. Never seen him do it but he probably can."
If he didn't display it/imply it, he doesn't have it. Period.
Besides if all else fails, he can't stop C4.
and P.S. Sorry if anything sounds dickish on my part. Thats not my intention. This is all still friendly debating