Challenge Mode/Superman Godfall/Nightmare/Challenge Battle 5

Doomsday is required in all matches of challenge battle 5. There are three possible characters you could choose: Doomsday/Regime, Doomsday/Prime and Doomsday/Containment. While Regime Doomsday is given by the Starter Pack, he is a silver card and thus has much lower stats and he has a poor passive. Prime Doomsday is a strong card, and he is always available for purchase (while Containment Doomsday can only be found rarely in Challenge Booster Packs and the Most Wanted Pack, if you haven't unlocked him from his challenge over a year ago; it is not practical to try and get him solely for this challenge), so he is the best to go for if you don't have a good Doomsday card already.

While some players may find challenge battle 1 (bronze only) and 3 (silver) to be harder due to the lack of strong bronze or silver cards, challenge battle 5 is generally seen as the hardest with one exception: Raven/Prime. The power of her passive at any level cannot be overstated and will make nightmare challenge battle 5 much, much easier for any player.