This morning the International Version of the Marvel Tsum Tsum Mobile Game was updated to add Red Skull to the battle menu for the first time!
He will be available until the end of the day (Pacific Time) February 21st.
When you play against him, he will sometimes throw grenades that you have to clear with bombs or skills. They have a timer and if you don't destroy them before the timer expires they will blow up and cause you a lot of damage. The newest orb box Tsums (Captain America Sam Wilson and Ironheart) have special advantages against Red Skill. Captain America Sam Wilson will clear all of the grenades with a single skill usage while Ironheart's ability will reduce the amount of damage the grenades do.
Here is a preview video of Red Skull's skills (when using him as your Leader)