Been reading up on some Hajime No Ippo, and I eventually got to where Ippo fights the boxer Ponchai Chuwatana. At one point, Ponchai throws a punch that literally leaves Ippo's forehead smoking. Ippo then also claims that the punch burned him. Now to find out how much energy it takes to really do something like that.
However, this source says that it only leaves a "burning sensation". This source also states that a First Degree Burn can occur at 118 degrees Farhenheit. I would assume that, under some circumstances, that a First Degree Burn can actually leave the skin smoking. Not only that, but nobody made a big deal over the burn in the fight, not even Ippo. He just noticed it and shrugged it off. This implies that the burn wasn't serious, and more often then not, First Degree Burns aren't really a serious thing to worry over. So for now, we'll go with 118 Degrees Farhenhiet.
EDIT: So I've been informed by Gwynblieddd that the way I calced this doesn't really work, and so he made a clac of his own which I will now put here. So everything from this point onwards is his work.
Thickness of human skin on forearm = 1.3 mm = 1.3*10^-3 m (varies at each part of the body but not enough to make a difference)
The area of the burn should be around the same as the area of a human fist ~ 40 cm^2 = 4*10^-3 m^2
Volume of burnt skin = Area*thickness = 5.2*10^-6 m^3
skin should be around the same density as water (1000 kg/m^3)
mass of burnt skin = volume*density = 5.2*10^-3 kg (5.2 grams)
average heat capacity of human body ~ 3500 j/kg*K (couldn't find the value for the skin so i'll use that)
ΔΤ = 48
Q = mcΔΤ
Q = 873.6 Joules (Street level)
(Gwynblieddd's calculation) Ponchai Punching Power - 873.6 Joules, Street Level
So no real buff, but still neat nonetheless.