Hello Welcome, This Achievement requires you to Total a car.
As the title suggests This achievement is specific to Mondays only
(for real) you can only attain this when it is Monday Wherever it is you may be. Moving on, apart from that slight obvious and funny bugbear it is pretty straight forward as all you need to do is to terminally damage a car and the achievement is yours.
If you’re anything like me then the car will spend half the time on its roof anyway and probably be terminally damaged at some point as a result, although (and I know it is not rocket science) I have added a quick and guaranteed way to kill your car: just to save you from that added measure of aiming for trees in those stages
This can be attained away from competitive play; From main menu go to Events - Joyride - Freeroam, you CAN pick any vehicle class you want (I advice preferably Rallycross as they are agile and easy cars to destroy in a straight line) once in Freeroam simply go full speed towards a wall and there you have it, a classy 5gs.
Good Luck and have fun racing.
P.S - Just before I tested this achievement for sure on another profile, Bonxy in the comments had earlier confirmed that the Developers said this is a (-Monday-) only Achievement. Thank you for sharing.
All the best, take care.