Well, a word by word translation would be: Μόνον ο Θεός μπορεί να με κρίνει
However, a very common phrase in Greek is "Let God judge me" and I think you should use this one. In capital letters: Ο ΘΕΟΣ ΑΣ ΜΕ ΚΡΙΝΕΙ
And as Nickel already told you in the question you posted in Proz.com:
Ο Θεός θα με κρίνει = God will judge me
At this site you can find :
μόνο ο Θεός θα με κρίνει (only God will judge me)http://flammablesubstance.blogspot.com/2005_07_01_flammables
but it would be more effective (in Greek) without the 'only'
My preference is for: Κριτής μου ο Θεός (God is my judge)
which is similar to Μάρτυράς μου ο Θεός (God is my witness).
Κριτής μου ο Θεός (God is my judge) is actually the meaning of the name 'Daniel'.
Ι agree with Nickel that you should go for:ΚΡΙΤΗΣ ΜΟΥ Ο ΘΕΟΣ