Micro-Oxygen

Micro oxygen is oxygen atoms that are smaller than normal, and can pierce any material.

Down at the atmoic levels, all matter forms a mesh. When Micro-oxygen is introduced, it slips into the mesh of atoms. When it is forced at at high pressures, it has enough to force to cause the decohering of the surrounding atoms, thus disassembling the target, and also violently reacting with any surrounding component substances, which would create cumbustions.

To put in simple terms, the blast cuts through it, and reacts with anything that happens to be in in the immediate vicinity, thus being an extremely effective weapon.