Deva Pain with low diff, if he wishes to one shot him with CT and higher difficulty, if he desires to play around with him. Anyway...
Rinnegan, possessing better insight than Sharingan, would allow Pain to see when Sasuke will cast Amatersu, leaving him prepared to Shunshin out of Sasuke's sight. He can, in addition, make it rain which will allow him to sense too. So, this isn't a problem. Susanoo Arrows are dodged as well, because one is basing this logical conclusion, which can be examined that the arrow travelled at the same speed as FRS, which Pain dodged at point-blank range.
Sasuke's main fire-power are Susanoo and Amatersu, which both fail to accomplish anything. Amatersu is either repelled or removed with a black rod, so it poses no threat. Susanoo can either be locked inside an CT, which it can't break from it, or it's finished with Biju Shinra Tensei. On the side note: the Biju ST would bust Susanoo clean at level 3. This is because it took out 3 toads - 2 whom are dead and Gamabunta is immobile. Gamabunta tanked few of Shukaku's Futon attack, which are undoubtedly more powerful than Danzo's powered up Futon, just by judging the sheer AOE.
-Ocular Genjutsu cannot work on Rinnegan.
-Elemental techniques are repelled.
-CQC is a suicide as stated.
Scenario 1: Pain low diff.
Scenario 2: Still low diff.
Scenario 3: Still low diff.
If you wanted to make it competitive, I suggest you restrict CT; although Pain would still win, but with greater difficulty.
