*I appreciate all up-votes. Considering this is the most recent and up-to-date solution, we should try and get this to the top.
8th June 2020: I'm going to clear this up a bit and give an update to how to get this achievement in 2020. You can do this level by level or in 2 runs.
The reason I have added step #2 is because me and my coop partner noticed that when we went through a level on Easy difficulty (originally going through because of Par-Time achievements) is that our achievement trackers for specific achievements started to increase. Testing and following the other steps, we noticed that this specific achievements tracker also started to increase.
If you have already played through both difficulties before attempting this solution, try from step #5 onwards and see what results you get. If this doesn't increase the tracker, follow from step #2.
Step #1: Play through all missions on Legendary with whatever 0 scoring Skulls you want. You'll complete the campaign without unlocking any level specific mission complete achievements and the tracker still at 0%.
Step #2: Once your Legendary run is complete, start again and play the first mission on Easy with NO 0 scoring Skulls active - Make sure you also look at the level in Classic Mode to just in case.
Step #3: Once you've completed the mission, you'll unlock the specific mission complete achievement and the next mission will load.
Step #4: Once the new mission has loaded. Save/Quit/End Game once you have control.
Step #5: When you're back at the main mission select screen. Load up the mission you just completed on Legendary with NO 0 scoring Skulls active.
Step #6: Once the mission has loaded, wait 10 seconds just to be safe and then Save/Quit/End Game.
- You'll now notice that this specific achievement tracker will increase.
Step #7: Now repeat steps #2-6 for the rest of the missions until the achievement unlocks or steps #5-7 if you have already done the previous steps prior to this solution and if it works.