So the fastest method that I have found to do this one is absolutely going to destroy your in-game Win/Loss Ratio but we're just here for the achievements, right?
Now to the even more unfortunate news.. You can't do this unless you have a friend or are able to find someone off of an Steam Gaming Session post - You can't accomplish this solo.
How you do this is you invite whomever you're playing with (Only need 1 other person) and you search for Teams Mode or Co-op Vs. AI. Once you load into the game all you and your teammate need to do is keep walking off of the edge of the map until your team loses, this should take all of 20 seconds to accomplish once loaded in. Thats it. Repeat that 500 times for the final achievement. Not super exciting but WAYYYY quicker than playing regularly.
Unfortunately Custom games do not count towards this achievement to anyone wondering.