He would take down a lot of characters. Many Kage level shinobi would fall to him. Because you cant put him down and he puts you down before the fight even starts for you.
The strongest guy he can take down?
I'd say Killer Bee is a possibility. Killer Bee wouldn't know he's immortal he would probably destroy Hidan in CQC thinking he's dead Hidan would land an unsuspecting blow on him, and then create as much distance as possible draw his circle (although he probably has it drawn before he engages Bee).
For Hidan facing Shikamaru was worse than if he faced some other Kage level shinobi. Shadow Binding and his analytical ability works wonders against Hidan.
basic sharingan genjutsu would end hidans career
Not really, Hidan would probably stab himself out of it. For example remember the scene where Itachi had Deidara almost blow himself up? That would be counterproductive against Hidan as he would follow through with attacking himself anyways....and then the pain would break him out of it.
