Blood Brothers

The Blood Brothers are mercenaries and villains.

History
The Blood Brothers ambush Hulk at the top of Stark Tower until Captain America, Falcon, Hawkeye, and Iron Man arrive. When the Blood Brothers have Hulk pinned down, they attach a device to Hulk's back that siphons Hulk's gamma energy which caused some of the Avengers to be infected with an unstable gamma energy virus.

The Blood Brothers contact Red Skull to tell them that their mission was a success. Red Skull cuts off the call from the Blood Brothers when they start to ask about their payment.