Doomsday/Prime

Doomsday is a destructive character. While his base stats aren't terribly high, his passives allows him to regenerate large amounts of health and keep on fighting, essentially giving him up to two life bars and making him excellent in absorbing damage early in the match. His powerful regeneration makes him a great asset in low level play, being able to heal significantly without using gear or hampering his damage output.

Strategy
He is one of the few characters with access to unblockable chance on basic attacks on their specific gear. Building basic damage/crit on him is a good idea, and will also make him resistant to Killer Frost/Prime's power dampening since he could essentially heal efficiently with basic attacks. Teammates that grant increased maximum health synergize well with his passive. Since to make the most use of his passive, Doomsday has to deal two knock out blows, a great set up would be a maxed (E7, level 50) Doomsday teamed with two support teammates at E0 (good choices would be, for example, Harley Quinn/Arkham and Lex Luthor/Krypto), which allows Doomsday to easily be the main damage dealer.

Doomsday is an excellent card for new players: one of the very few cards to have a strong, practical innate self-heal which gives him great strength both in single and multiplayer. When starting to evolve gear, he could focus on more basic attack damage to mow down his opponents faster while most other characters will be forced to dedicate some effort to heal self gear.

His passive is also really nice for anyone who needs a tank card. As stated, he can at max, have 200% of his normal health. His health stat is decent to begin with, although his damage stat could be greatly improved, and would have to be to make this a good card for competitive play.

Due to his strong basic attacks and large heals that do not require specials to be used, Doomsday is a great character to use to complete "without blocking" and "without using specials" Bonus Missions.

Abilities
Here are Doomsday's abilities.

Support Cards and Gear
Here are Doomsday's support cards and gear.

Trivia

 * Doomsday's special 1, Ultimate Liftoff, is based on the "Upward Venom" move from console. Earth Shake is based on the move of the same name.
 * Strangely enough, if you're fighting against him, his light basic combo will be actually be Doomsday/Regime instead; on the other hand, if the player is using Doomsday Prime, this time it will be him his own light basic combo.