Here are the settings I'd recommend:
Mode: Total Chaos
Number of Players: 1
Weapon: Singularity Bomb
Building Collapse: High
Rounds to Win: 5
Your main goal is to attempt to destroy the entire Complex map. To do so, run around the outside of the map following the edges of buildings, leaving a singularity bomb at each building corner. Use the Rhino Pack when moving along from corner to corner and between buildings.
Drop a bomb at the edge of the stack when you run by as well. If done right, this nets 150k to 190k points each time.
This achievement is not difficult, but is extremely tedious. Using any other map besides complex means a much lower score and a much longer time to net the achievement. Also, setting the number of rounds to 5 means less loading time to start the map in between games.
As a side note, you might want to first do the achievement Can't Get Enough, which involves playing all modes on all maps in Wrecking Crew. This will not get you that far along, but will save some of the tedium at least. Expect to spend around 200 minutes (around 3 hours) of doing the same thing, minute by minute to get the achievement.