By the time the player acquires the Atom Smasher, there is little use for it; the player is on their way to procure the item that lets them reach the final boss, and they have already acquired the Neutron Blade and the Laser Lance, and possibly levelled up the former. Compared to these two weapons, the Laser Lance has ranged charged attacks and the Neutron Blade has faster attack speed than the Atom Smasher and multi-hitting charged attacks. The Atom Smasher is also not needed to break down any barricades or obstacles.
The Atom Smasher's level 2 attack is to step forward while swinging overhead twice. Its level 3 attack has the Hero throw the axe, which circles around him slowly and then returns to his hand.