In Naruto Chapter 551, Naruto, Killer B, and Itachi's combined attack make a huge crater.
Mountain Height = 609 Meters = 217 px
609 Meters/217 px = 2.8 Meters per px
Crater Diameter = 500 px = 1400 Meters
According to this calc, crater depth for craters over 150 Meters are 0.18x the Diameter.
Crater Depth = 252 Meters
Volume of Crater (Spherical Cap) = 202341086 Meters^3 = 2.02341086e+14 Cm^3
There's smoke and the attack was partially done by a Bijuu Bomb, which we accept as vaporization
(2.02341086e+14 Cm^3)*(25700 Joules/CC) = 1.2 Gigatons (Large Mountain level)
Naruto, Killer B, and Itachi did this together, so they each scale to 1/3 of the result
Naruto, Killer B, and Itachi's AP = 414.3 Megatons (Mountain level)
Yeah... Didn't think the result would be this high... I'm like 90% sure this rating won't last, but hey, I did my best 🤷♂️