Loki dominated an amped Harald, someone whom Imu could not even fathom ever losing. Imu would not even give Roger or Whitebeard a second glance in God Valley btw, they were inconsequential in the grand scheme of things for him.
Loki is unquestionably above Kaido as well. Kaido’s introductory feat, the defining moment of his hype, was replicated by Loki when he was still an infant. And it was not a one time thing either. A child Loki kept replicating that same feat over and over again. How can people still fail to see what Oda is doing here? Loki is by far the strongest child we have ever been introduced to. The child versions of Kaido, Oden, and Big Mom cannot even compare to Loki’s day one feat.