I'm doing this JUST in case someone wants to calculate a feat like this

This only will apply if the "victim" is a regular human... for obvious reasons

The average volume of a human head is 2912 cm³, so keep that in mind and the density is like 0.8072 g/cm^3 </span>

There are remains of the head

Fragmentation: 4.4 J/cc

The feat will at least get a value of: 

4.4 x 2912 = 12812.8 joules

There are very few remains of the head

Violent fragmentation: 7.533 J/cc

7.54 x 2912 = 21956.48 joules

The head is not there at all

Pulverization: 12.9 J/cc

12.9 x 2912 = 37564.8 joules

So, at least like Wall level...