I have found I can't even drag a deer downhill without paying for it later (bad hips and back fusion gone wrong). I have my 4 wheeler for normal retrieval but what if one falls into the bottom of hollow that is not accessible with a 4 wheeler; Enter the Deer Drag-A-Matic 600, patent pending of course, he says tongue in cheek.
A 600 lb boat winch, 80 ft of 1/8" cable, a ratchet strap to secure the winch to a tree, a 20V lithium drill driver with a spare battery and manual hand crank as an optional source of power. Don't know if it will work but I suspect it might. Total cost less the drill driver, $24.
If the drill driver doesn't have enough power I have matching impact wrench (seen in the picture) that puts out 250 ft # of torque that surely will.
OK a nutty idea but there are some areas I like to hunt (walk in only) that the impossible deer retrieval has kept me away.