NOTE: Up until the april 2016 title update this was unobtainable.
After the update, it's obtainable but only ON A NEW SAVE FILE. If you have an old save and don't want to delete your progress, see Unobtainable achievements status: All achievements now obtainable!
. Credit for the new save file find goes to o NexusPlexus o
Snakes start popping up as an enemy after the boar has been introduced, around the 9th mile on endless mode.
The easiest way to get a kill by snake is with a boar. Stand between the boar and a snake, wait for its little jump tell that it's about to charge and then sprint out of the way with
. You can also scare wolves into snakes with
It takes two snake hits to kill a boar, three for a wolf and the bear seems to be unkillable by snakes.
You can also craft a torch and use it to lure snakes towards you. Since the torch also scares away animals, I find it generally trickier to use for kills by snake though.