Cities: Skylines

Quickest way to get this achievement:

•Start up any scenario
•Delete all the roads on the map (if any)
^if none just built a section of a road then just place wind turbines till you're out of money.
•Once all that's done just set the fast forward to x3 and just wait till the failed scenario comes up then choose restart and do the same thing 4 more times. (Confirmed from Jumbo91375)


☆Jimbo91375 confirmed that you can restart the same scenario and get the achievement.
☆When doing a scenario you can do all the different types of disasters to earn the corresponding achievements for them.
☆The "What The ?" Achievement is special tornado that randomly pops up so that can take a couple hours or even more. I'll recommend doing that on a regular map, a dummy map, instead of your main map.
☆The disasters don't start right as you choose them (there will be a cursor placement where you want the disaster to be at. There will be a message about a meteor, tornado, earthquake, etc coming in. The bottom of your screen will show yellow and black markers on top of it like you're about to destroy something.

Another quick option I did.

Load up Alpine Villages Scenario.
Delete the highway connected roads.
Dezone the map
Set speed to x3
Wait.

Then repeat!

Already two good guides here but thought I'd give another option for anyone who has the Green Cities DLC, and you can literally get the achievement in about 2 minutes at most.

There is a scenario added with Green Cities called Clean Up Crew, and one of the losing conditions is to have a population less than 1.

Simply start up that scenario, click and hold Left Stick to move up to 3x speed. Press X to open the demolish tool, and press D-pad right three times to maximise the area of effect. You can then simply hold down the A button and brush over the entire map area to demolish all of the houses and roads. The population will plummet to zero in no time at all, and you can then just restart the scenario and repeat another four times.