When you say Pain(nagato) do you mean the 6 paths of Pain or just the single body nagato??
Please specify a bit more..that is whether nagato is healthy or not, intel, distance, restrictions etc.
Raikage will probably be able to take down most of the 6 paths but Deva path will be the most troublesome as always.
Leaning towards a Nagato very high difficulty win for now.
Raikages spear will be negated by chakra absorption mechanics, also there is always CT to fall back on.
If you also permit the Gedo Mazou Nagato's win will come down to high difficulty.
a/third & b duo would be better match up against nagato, and yes you should give more info about restrictions nagato got red rinnegan in battle against naruto and bee, do he have that ? sage eyes