So far this is my favorite deck to use for the "Destroy 8 Cards" bounty. It's not a one-and-done deck, nor is it the best destroy deck, but it will get the requisite 8 kills every 2-3 games, has a reasonable chance of winning, and most importantly is a hoot to play.
You will know if you've reached the necessary kill count when death is free. And of course a 0/12 is a fantastic Moon Girl target.
THE CARDS
Deadpool: a 1-cost that can re-enter play after being destroyed. He's great to get out early but that's not the point of the deck.
Nico: a 1-cost that can kill cards, destroy cards, create a 1/6, give you a card copy, or add +2 to a card (ideally X-23 or Deadpool, but anything will do)
Squirrel Girl: 3 1-cost cards in 1. Great for Killmonger or Marvel Boy.
X-23: another 1-cost that can die and not go away. Also a great way to preserve Marvel Boy bonuses and get just a rich more energy.
Carnage: Carnage is here to destroy cards.
Kate Bishop: A 2-cost that puts two 1-costs in hand.
Marvel Boy: Marvel Boy is here to add power to your 1- cost cards. This can be a setup for Knull or a win condition in its own right. You don't really want to destroy him with Carnage or Venom, but it's not the end of the world if you do.
Killmonger: Killlmonger is here to destroy cards. He is probably your best tool for pushing up the destroy count and your only offensive destroy tool.
Venom: Venom is here to destroy cards and preserve their power.
Moon Girl: One of the inspirations of the deck. Good for getting a 2nd Death, 2nd Knull, or 2nd buffed card (often Deadpool or cloned Venom).
Knull: Kull is the reason why you don't mind playing Marvel Boy and Killmonger in the same deck. He is power preservation.
Death: The other inspiration for the deck. Good cheap power and your yardstick for determining if you've met the bounty condition.
SUBSTITUTIONS
Shanna: possible substitute for Kate Bishop or any of the 1-cost cards. However, she does present inherent risk because of the possibility of summoning Bast.
Wiccan: possible substitute for Marvel Boy. There will be less power on the 1-cost cards, but it'll be easier to get two Knulls in play.