The first "Chop2Shop.Zom"
you will come across is right after you received the first call from your mom in the PROLOGUE
level. Enter the shop, scroll down to "AWESOME SKILLZ"
and choose "CHAINSAW STAB"
medals, buy it. Now exit the shop and simply do the combo:
Chainsaw Stab =
The achievement should unlock right away. If not just try it a few more times. You only have to use it. No need to hit a zombie with that.
Best Regards,BLAZE VII
Here is a visual guide for everyone who needs it:
Credit goes to *savgcom*