There will be two cases:-
1.One is moving one is stationary.
2.Both moving.
So how will you decide which car intentionally hit another, well OnTriggerEnter will not help obviously.
You can check the speeds of both cars in two cases
In 1st case its pretty simple the one having speed hits the other.
but its tricky for 2nd case , you can say car with more speed intentionally hit other though its not always true but it will work most of the time.
use,
GetComponent<Rigidbody2D>().velocity GetComponent<Rigidbody>().velocity I hope this is what you want :)