If you descibe someone as an
Infernal Iconoclast, you are implying that they are extremely
irascible and they are just a thorn in your flesh and the bane of your life.
Origin: Infernal - Very annoying.
Iconoclast- Someone who attacks cherished beliefs or institutions.
So basically you are depicting the person as annoying as a housefly, which always "attacks" you and makes your existence miserable (Infernal & Iconoclast).
Conrad: Do you know what's the most annoying thing in your life? Getting all your hard-earned game data erased because you accidentally
uninstalled it!! All beacuse of the Developers!
Belotte: Those
Infernal Iconoclasts!