Is there any diprotoic acid where both pka's are less than 0?

The question states it all. 


I'm working out special cases for a different problem and such an acid would create another special case. 


Sulfuric Acid is the strongest that I remember. pKa's −3, 1.99 




[Ethanedisulfonic acid](https://en.wikipedia.org/wiki/Ethanedisulfonic_acid) does indeed have $pK\_{a1}=-2.06, pK\_{a2}=-1.46$.


Using polycyano substutution can also work. [This paper](https://www.semanticscholar.org/paper/Absorption-and-Fluorescence-Emission-Attributes-of-Zahid-Grampp/8051ea512f0de38e77396366007cddd540ec223a) reports the table below, note that the tetracyano hydroquinone "makes it" (in the excited state produced by irradiation).


![enter image description here](https://i.stack.imgur.com/5DqCd.png)


 6