My hardest rival was number 4- it took me 3 and a half months.
Actually beating the guy was the easy bit, but trying to get all of the challenges to go up against him had me in tears.
My story on that; I had used every car in my arsonal try to get bounty, etc. I was down to my last car when I finally got the required bouty, etc, and went on to defeat number 4.
So, when I got my big pay out for that, I immediately got all over my cars out of impound. lol!
That was my finest hour on this game so far.
CROSS, you ain't stopping this, you can't touch this, YOU CAN'T SEE ME!