Sinistrad

then whats the hardest substance?

I believe, if the question is "What is the hardest substance in the universe?" then the answer would be:

The hardest known substance in the universe is the crust of a neutron star.

http://www.sciencedaily.com/releases/2009/05/090506110202.htm

Of course, that does us little good as it derives its strength from gravity. If transported to Earth, the substance would explode as the electromagnetic force repelled all the particles from eachother. No Neutronium for us, I suppose