Lady Loki, Agent of Chaos

Whenever you cast your first instant, sorcery, or Villain spell each turn, exile it, then exile cards from the top of your library until you exile a nonland card. Lady Loki deals damage to each opponent equal to the difference between that spell's mana value and that nonland card's mana value. You may cast that card without paying its mana cost.

Ultimo, Civilization's End

Menace (This creature can't be blocked except by two or more creatures.)
When Ultimo enters, each opponent sacrifices a creature of their choice.
{2}{B}, Discard this card: Each opponent sacrifices a creature of their choice.

Experimental Armor

Equipped creature gets +1/+1 and has flying and haste. (It can't be blocked except by creatures with flying or reach. It can attack and {T} as soon as it comes under your control.)
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Furious Strength

Enchant creature
Enchanted creature gets +2/+2 and has menace. (It can't be blocked except by two or more creatures.)

Happy Hogan, Dauntless Driver

The Immortal Weapons

When The Immortal Weapons enter, return target instant or sorcery card from your graveyard to your hand.
Whenever you cast a noncreature spell, target creature gets +2/+0 and gains menace until end of turn. (It can't be blocked except by two or more creatures.)

Marvelous Melee

Marvelous Melee deals 6 damage to target creature.
Basic landcycling {2} ({2}, Discard this card: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.)

Copy

Living Laser

Haste
Whenever Living Laser attacks, for each card you've discarded this turn, create a token that's a copy of Living Laser, except the token isn't legendary. The tokens enter tapped and attacking. Exile the tokens at the beginning of the next end step.

Quicksilver, Pietro Maximoff

Haste (This creature can attack and {T} as soon as he comes under your control.)

She-Hulk, Jennifer Walters

Trample (This creature can deal excess combat damage to the player she's attacking.)
{2}{R}, Sacrifice a land: Draw a card and put a +1/+1 counter on She-Hulk.

Smashing Spree

Target attacking creature gets +3/+3 and gains trample until end of turn. (It can deal excess combat damage to the player it's attacking.)

Wiccan, Young Avenger

Whenever you cast a noncreature spell, exile the top card of your library. Until your next end step, you may play that card.

Colossal Collision

Put a +1/+1 counter on target creature you control. Then that creature deals damage equal to its power to target creature an opponent controls.
Basic landcycling {2} ({2}, Discard this card: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.)

The Fabulous Frog-Man

Reach (This creature can block creatures with flying.)

Loki's Scepter

When Loki's Scepter enters, gain control of target creature until end of turn. Untap that creature. Until end of turn, it becomes a Villain in addition to its other types and gains haste.
{T}: Add one mana of any color.

Feral Ferocity

Target creature gets +4/+4 until end of turn.

Marvel Super Heroes Commander