This doesn't have to be done in the career mode.
Just pick a quick game, go to "england", "track 1" (looks very short) and put the other drivers on "very hard". You just might up being last, even if you try hard not to
I liked driving around with other guys rather then against the clock, so you get to see your position all the time. Don'T wanna race against the time and find out that you are not last.
A round takes about 30 secs, 6 rounds... Quick achievement!