So, dragons here are smaller (somewhere at around the size of a shire horse), and more agile creatures, relying on their wits, speed and insane firepower. They are tougher than giant pterosaurs, and maybe even bears, still, they aren't invincible. You sorta have to do that if you want to create tension for a dragon protagonist without seriously nerfing them.
I know this overwhelming firepower is supposed to be a breath weapon, and that it has a secondary ability that destroys nano and micro machines on contact. Just to be clear, firepower should mean ability to destroy... mostly anything. So, special viruses/bacteria/toxins won't cut it.
Since being able to immolate even the high echelon of The Circus is the second most important factor for balancing dragons, I'd like to, know what's the strongest "weapon" a creature's body can produce, that meets the criteria?