lol, no, its not. Using your best move=/=High difficulty. Difficulty is how hard it was to win the fight (Or to do anything in a general case), nothing else.
If he uses his strongest move but absolutely rapes someone with it, is it high difficulty? No.
He could probably even beat him without the use of Shinsuusenju. Hashirama's techniques require Nagato to use his upper leveled techniques to counter. CT is never happening from the start with manga intel and the fact that Nagato will need to expend Deva to survive a second against him and Preta can't even absorb Mokuton.
-Hotei no Jutsu creates giant Mokuton Hands that
You must be registered for see links
These hands each dwarf Nagato and make him look like a tiny ant in comparison. He would need CST to obliterate all these at once as Hashirama can send them one at a time. Sending them one a time allows Nagato to counter the first one with Shinra Tensei, but he won't be able to counter the rest of them due to the 5 second time limit. Result? Nagato gets crushed like a bug.
-
You must be registered for see links
spawns for miles and releases sleep pollen. Nagato WILL need CST to destroy this which leaves him without Deva's abilities for some time.
-No attack Nagato has is getting past Hobi no Jutsu
You must be registered for see links
.
-
You must be registered for see links
is another technique he'll need to use Deva to block.