Ikusa-Tsunagi creates a huge crater with his sword slash. The slash isn’t finished in the image below, it keeps extending to the horizon in said image and even reaches the water, which is nowhere to be be seen in the shot where we can see the slash, proving how the slash continued that much farther than what was shown, so as a lowball, I’ll assume the length in the image I use is only ½ the full crater length.
Average Human Height = 1.7 Meters = 1 px
1.7 Meters/1 px = 1.7 Meters per px
Ikusa’s Height = 1284 px = 2182.8 Meters
Ikusa’s Arm = 892 px = 1516.4 Meters
Ikusa’s Arm = 1516.4 Meters = 54 px
1516.4 Meters/54 px = 28.08 Meters per px
Half of the Crater Length = 625 px = 17550 Meters
Crater Width = 74 px = 2077.92 Meters
I’ll assume the depth of the crater is at the very least ½ as long as the width
Crater Depth = 1038.96 Meters
Full Length of the Crater = 35100 Meters
Triangular Prism Volume = 37888300000 Meters^3 = 3.78883e+16 Cm^3
Pulverization of Rock is 214.35 Joules/cc
(3.78883e+16 Cm^3)*(214.35 Joules/cc) = 1.94 Gigatons (Large Mountain level)
Result change is very minor, but I have fixed it in line with Alex's instruction