In Marvel Puzzle Quest, you get a lot of choices for your team. It is important to know which cards are just THE WORST.
With this in mind, most of these cards can be really great but only if you have a good support team.
Let's look at the first card: Carnage. Carnage is not someone you ever want to go against in PvP or PvE. However, unless you have someone on your team that gives true healing, you won't be able to play very long without losing a lot of your team's health if he was on your team.
Carnage is an equal opportunity card. For every time he does a move against the enemy, the move is done to his allies. His Alien Instincts (black) power creates friendly and enemy strike tiles. As his level goes up, their strength goes up. Symbiote Scythes (red) power attacks the target at a high damage, but also attacks everyone else at a lower damage. At high levels that is over 2000 damage to your teammates.
Use it well and Carnage is a beast on your team. However, if you don't prepare carefully, then he can easily ruin his own team's chances.