Just as a note, this did not unlock for me when i got Super Nova for getting all stars. I had done the Kingmaker race as soon as it was available and it for some reason did not count, so after i had finished everything i had to do it again. So either try saving it for last, or just redo it again to pop the chievo.
:Edit: this worked for me, another said he just hard reset and it unlocked, so try either or and you should be aces :D
:Edit: some have had success with these and some have not, unfortunately at the moment it seems like a toss up whether or not these methods will work and there has been no definite way to unlock this it seems all we can do is either wait for a better workaround or patch :( sorry to all those who are having problems, i just started this as a heads up but it has turned out to be a pretty glitchy nightmare for a lot of people it seems