The weapon has a unique design with the hammer head comprised of four fusion cores instead of the regular plain steel block, giving it a much more massive overall look. Said cores appear to have been deliberately damaged in order to leak glowing green radioactive material from the contact area, which is most likely the source of the immense amount of radiation damage the hammer can inflict. When swung or simply held in hands, Atom's Judgement emits a sickly green vapor from its head that leaves a smoky trail whenever the weapon is moved in any way.
Contrary to other unique melee weapons, like Kremvh's Tooth, whose effects originate from a special physical modification, Atom's Judgement's properties are in fact provided by a unique legendary effect of the same name. Because of this mechanism, the modifications for a super sledge can be applied, but the radiation damage effect cannot be removed and applied to other weapons.
Atom's Judgement is arguably the most powerful melee weapon in the game, capable of inflicting ludicrous amounts of damage far in excess of what a standard super sledge can dish out. Maxing out all perks that increase the damage of this weapon will allow the radiation damage to exceed 890 radiation damage. While most creatures and animals are immune to the radiation component, human enemies don't stand a chance no matter how heavily armored they might be.