Crime Boss: Rockay City

By completing this achievement, you will also automatically complete "Dragonslayer" (defeat green gang), "Off the rocks" (defeat yellow gang) and "Raider's Ruin" (defeat red gang).

It's probably impossible to do this in the first run of the campaign. However, I was able to complete it comfortably with boss level 35 in the third run (for reference).

Be aware that conquering the 30th turf ends the campaign, as it is a possible end to the game. You will get the achievment only when you click on "Finish the campaign" instead of "Finish the day". Make sure you really have all 30 turfs colored blue and none grayed out under the control of detectives.