Feat: The Pyro survives a building-sized explosion.
To figure this feat out, I'm going to need to determine the height of the Building's windows where the explosion occurs. To do that, I'm going to take an earlier scene in the comic where a proper comparison can be made:
Robot Scout: 51.16 px Robot Scout should be the same height as the Scout, who is 70 inches (1.778 m)
Height of the window: 56 px
Height of the Window in cm: (56 / 51,16 px) * 1.778 = 1.946 m
Now that we have the height of the window, we can compare it to the height of the explosion. Fair warning though, I had to do a bit of eyeballing with where the explosion ends due to the text bubbles cutting off the top part of the explosion.
Height of Window: 49 px
Height of Explosion: 496 px
Height of Explosion in m: (496 / 49) * 1.946 = 19.700 m
Based on the information from this blog , the explosion yield should be a 20 psi overpressure explosion, since the top half of the building is visibly blown off (for some reason the windows weren't destroyed, but whatever).
The formula used for surface explosion/overpressure explosions is W = R^3 * ((27136 * P + 8649)^(1/2)/13568 - 93/13568)^2, where W is Yield in Tons of TNT, R is radius in meters, and P is pressure in bars.
Explosion Yield: W = 19.700^3 ((27136 * 1.37895 + 8649)^(1/2)/13568 - 93/13568)^2 = 0.615 Tons of TNT
This is actually consistent with the energy yield that the Cow Mangler has, and since Pyro is Pyro and all of the RED Mercenaries are at least somewhat comparable to each other, they all scale to this feat. Same goes for Saxton Hale as well as he should be above the RED Mercs.
EDIT: Ok, since the explosion isn't nuclear, I actually have to divide the yield of the explosion in half since half of the energy from an explosion is from the blast itself.
0.615 / 2 = 0.3075 Tons of TNT
Even when divided in half, this feat is still consistent with both the Cow Mangler's energy yield (0.7 Tons of TNT) and Scout's three explosion feat while badly injured (0.1 Tons of TNT), so this feat acts as a nice middle ground.