Suggested by Lethal_Gecko
The Warden Eternal from Halo 5 will go up against MCU Ultron.
Battle takes place on current day Earth. No leaving the planet but the Warden has access to the domain. Depending on outcomes, different versions of Ultron can be used in ascending order of power. The victor is whoever eliminates the other entirely, or other forms of submission are viable, like working together.
Who will win?