Company of Heroes 2

Good news, my fellow achievement hunters, because now you can get this achievement (including the rest of "complete 100 missions" in various ToW challenges) far easier by boosting with reloading mission end saves. All what you need to do is to, say, save the game in the first campaign mission at its very end before you deal the final blow with the AT gun to the Panzer 4, and just keep reloading it and finishing off the tank, which will count every time as one finished mission. This method wasn't working before, but it is in boosting skirmish games vs AI for some reason.

Ofc, you do this after you finish the game at least once regularly (and get the rest of related achievements to it), and just keep reloading as many times as you are needing to the 100. Same goes for the Theater of War co-op missions, challenges and the single player scenarios. You could get this achievement probably regularly if Relic continued to add more ToW DLCs, making it fresh and more interesting to invest additional time in it, or by playing far more interesting Ardennes Assault expansion campaign, but, unfortunately, last time I checked folks at Relic forgot to link that one with the achievement so the missions played in AA weren't counting towards it (I wrote the guide back in 2015).