What takes precedent, statute's of limitation or the level of the fraud?



Answers:
I don't understand what you mean 'level of the fraud.' The statute of limitations (not possessive) is always controlling. In criminal terms, it doesn't matter if it was a felony, it's still subject to the statute of limitations. In civil terms, it doesn't matter if they stole 25 million as opposed to $25--you're still bound by the civil statute of limitations.

Now, some jurisdictions have doctrines that extend the statute of limitations such as the discovery rule (the statute of limitations doesn't start running until you discover or reasonably could have discovered the fraud) or lulling (the tort feasor takes actions to make you believe they haven't committed an error), but these doctrines are limited.
There is no flexybility on the statute of limitation based on the 'level of the fraud' as you say. Once the statute expire it's over, no matter how big the fraud was.