LLC, S-Corp, and C-Corp all over roughly the same legal liability protection.
Maybe you were thinking of "Sole Proprietorship"?
The only scenario I can think of where an LLC or S-Corp might offer less liability protection than a C-Corp is in a post-bankruptcy situation. And that's more about tax liability than legal liability.
No I'm thinking S-Corp. I'm not sure how it works in all states but my understanding was that an S-Corp isn't even really a corporation, it's just a tax code classification. Whereas an LLC is a "Limited Liability Corporation" which does exactly what the title states, limits your liability. The fact that an LLC (and many other entities) can use the S-Corp tax accounting rules further leads me to believe that an S-Corp is just a tax shelter of sorts and provides absolutely no liability protection.