OK, this achievement has been the bane of peoples 100% completion for a bit since there isn't really information on how much better the skill level has to be. From my testing its roughly 450 to 500 skill difference.

Since the a recent update to the game, they let us reset our rank and skill. The Reset Stats button is located in the options menu. For this tactic to work, the server needs to record your reset correctly so it's going to be trial and error.

This is what my partner and I did to get this achievement. One of us would be already over (he was around 450 skill) if one resetted so I reset first and kept joining each others game until my stats stopped changing to the original numbers. This may take a few tries and even though it looked like it worked, rejoin the game again to make sure.

Once we were sure it recorded, I kept beating him 10 times and exiting the game. Took about 30 wins before it popped for me. Once I had it, my partner reset their stat and he waiting until I chopped around 800 to 900 chops in single player before losing. That put me around skill level 500. Then my partner with 0 skill beat me a lot, maybe 45 wins total before his popped.

Hope this helps some people.

- Note this is what worked currently. The devs might sneak a change in there since there isn't a specific number listed for the achievement so hopefully not because it was hard enough as is.