a) What is the mass of a .50 caliber bullet and how fast would it need to move do exactly that level of damage?
b) If I wanted my protagonist to do the exact same level damage with his fist, how fast would his fist have to be moving to do it? I get that his fist has more mass than the bullet so presumably, it wouldn't have to move quite as fast - but there's the issue of uneven consistency of substrate (bone, tendons, flesh etc) and the fact that the fist is attached to an arm and the arm to a body.
As to the protag himself and how he does what he does, he's a martial artist of rather ... extreme capability. Think Ryu/Ken from the Street Fighter videogames or perhaps Ranma as of the end of the series would be a more accurate comparison. I don't want to say "really low-end Dragonball Z" because that would be a turnoff for a lot of people. Ah well.
In any case, thanks to extensive training and meditation, the protag can manipulate his chi, basically his 'life-force' a spiritual energy that, while it mostly exists on a more existential plane, can be manifested physically in a wide variety of ways - one of which is a remarkable facility for converting potential energy into kinetic at ridiculously high efficiencies. By extension, it also has the very useful property of doing to kinetic energy what lasers do to light (hence the 'pink mist punch.')
Long and short, he can temporarily enhance his own strength, speed and durability to perform spectacular feats.
Any help at all would be greatly appreciated. Thank you for your time.