In the Kung Fu Panda TV show, KePa destroys the Jade Palace. Getting a clip or even a screen recording of the episode turned out to be more trouble than it was worth so just go to 18:15 of this link here:
Somehow even more annoying was trying to get a proper height for the Jade Palace. I'm not going to go over everything in detail, so hopefully the following images and math can explain everything well enough. If something needs clarification, let me know in the comments. I guess you should know, though, that Po is 6'2" and that I'm assuming the palace has a square foundation.
294 x 294 x 60 = 5186160 px^3
414 x 414 x 69 = 11826324 px^3
498 x 498 x 73 = 18104292 px^3
623 x 623 x 222 = 86164638 px^3
5186160 + 11826324 + 18104292 + 86164638 = 121281414 px^3
121281414/9 = 13475712.6667
13475712.6667 x 8.92718282354 = 120300150.653 cm^3 for the volume of the Jade Palace
But every pixel is (1.0081567923385627443800336425612 cm) so
Volume (cm^3) = Volume (px^3) * (1.0081567923385627443800336425612^3) = 124273489.48876496587537739334301 cm^3
There's literally nothing left of the palace after this happens. It was a firebased attack so let's call it a vaporization. Looks like it's made of granite.
124273489.48876496587537739334301 x 27050 = 3.3615979e+12 joules
Standard hollowness assumptions is 80% hollow so
3.3615979e+12/5 = 6.72319578134 x 10^11 joules or MultiCity Block level or 8A
This would be KePa's AP and since Po tanked attacks from him and defeated him, he would also scale. This would be for his second key.
And since he should be stronger in his third key than he is in his second key, he should be "At least 8A" in his third key. Kai would also scale since he fought Po in his third key.
ThePerpetual's Adjustment
The current math says that 9 pixels equals ~8.927 cm. That would make a single pixel 0.992 cm... or a cubic centimeter 0.9762 cm^3.
That said, I also took a look at that third picture... you seem to have measured both the height of the stair itself and its depth relative to us, rather than just the height. I took it into Paint really fast to check... and I only got 7 px for the height of the closest stair (which still probably lowballs the result a bit, since the Jade Palace is further away from the camera than said stair and therefore larger, but since that's not very solidly measurable... whatever.)




That would yield...
8.927/7 = 1.2753 cm
(1.2753^3) = 2.0741 cubic centimeters per cubic pixel
121281414 cubic px x 2.0741 cubic cm/cubic pixel = 251549780.78 cubic cm
x 27050 (the vaporization value for granite), x 0.2 (80% hollowness), and I get 1.3609e+12 Joules or MultiCity Block level or 8A