Today the International version of the Marvel Tsum Tsum Mobile Game was updated to add Chemistro to the battle menu!
He will be available until the end of the day (PST) December 14th so you have two weeks to battle him!
He has a unique ability when you battle him. He will summon a gun. When he summons the gun a countdown clock and a blue bar will appear next to his health bar. Damage you do will go to damage the gun instead of him and if you manage to destroy the gun before it fires you won't take any damage. If you don't manage to destroy the gun, the gun will fire when the timer expires doing a large amount of damage.
Here is the preview video of his gameplay: