In the case of 'reduce a human body to energy', presumably by turning it into gamma ray photons by one means or another, the answer is fairly straightforward... the average mass of, say, a North American is 80.7kg, and via $E=mc^2$ you get about 7.3 exajoules (about 1.7 gigatonnes TNT equivalent, slightly larger than the ecombined yield of the world's nuclear arsenals).
Your request, "free quarks and electrons" is somewhat harder because colour confinement prevents free quarks from being a thing at the sort of temperatures you'd expect to find in most parts of the universe these days. Very, very loosely speaking... when you try and separate them, the amount of energy you pump into the system is sufficient to create new quark-antiquark pairs which hook up with the quarks you were trying to pull apart, forming new hadrons.
You can avoid this issue by forming a quark-gluon plasma. You can do this by heating regular matter up to 2x1012K, at which point protons and neutrons will fall apart into their constituent quarks. Apparently an average human body (whatever one of those is) contains about 4.1x1028 nucleons, and the quark-gluon plasma temperature is equivalent to giving each of those about 140MeV of energy. This works out as about 920 petajoules, or a mere 220 megatonnes equivalent.
Given how hot the resulting plasma is, you'll find it will cool down extremely rapidly by releasing a lot of gamma rays and congealing back into regular plasma made of baryons, which will then expand rapidly (on account of being Quite Hot).
The end result, in either case, will resemble a large nuclear fireball, and devastation of the sort you'd expect to see from an asteroid impact or major volcanic eruption (such as the eruption of Thera for total energy conversion, or Krakatoa for the quark-gluon plasma).
Clearly, if you want to evaporate someone into nothingness, you'd best find a different mechanism (though I can't argue against its effectiveness on most targets).