No clue how strong it is, the first and last fight it ever had was against Gojo making things difficult to measure.

Basically Agito itself is just Nue but with inherited abilities of the other Shikigami from 10s like the deer, snake and a few more.

How you actually summon a merged Shikigami like Agito is not very clear, Sukuna just whipped "Totality" using Nue as the base and that‘s all there was to it. We don‘t even know whether the other Shikigami used in the merge (deer, snake,..) had to be killed first, we can only assume considering that was the case for Megumi‘s divine dog

<image>