Sawfly_Varte
Just make him use his Sitri Clan trait together with Imagination Magic to turn water into Oxygen and Hydrogen, He can use Oxygen and Heat control to create Fire, Oxygen Explosions and to Poison Someone by giving them Lung Damage; and he could use Hydrogen for a Hydrogen Bomb, for Ultraviolet Flames (Almost invisible fire is kinda OP imo), you could also go Big Brain and use the Hydrogen to make Hydrogen Chloride (Gas that when in contact to water vapor [Sitri Trait] forms fumes of Hydrochloric Acid) for acid attacks and Hydrogen Flouride (When in contact with moisture forms Hydrofluoric Acid and in Gas form can cause Blindness), and finally you could go Giga Brain and make a formula with Devil Magic to use Hydrogen as a bridge to the Schrödinger equation that you could 'use' in an anime sense as a door to Quantum Mechanic Magic.