After a considerable amount of research, it is my estimation that the Holos with the highest base power levels are Sora, Fubuki, Marine and Korone in that order. The base power level of these four appears to be so much higher the rest that it warrants putting them in a separate category. Note that base power level =/= max power level. It is possible, indeed probable, that there are more than a few other Holos with higher max power levels than any of those four. For a well known example of this, see how Vegeta had a much higher base power level than Goku during the Saiyan Saga yet Goku had a higher max power level. Exactly who these Holos with the highest max power levels are is something I am unable to determine as measurement of vtuber power levels is still a fairly new science based more on educated guesses than concrete facts. Any assistance in contributing to this field of study would be greatly appreciated.