The Bella Sisters
According to Capcom, they are two blind chainsaw-wielding sisters infected with Las Plagas. However, Leon and company must have 'shit-magnet' on their foreheads, since they can literally home in on their positions.
I hated fighting these inside the arena stage in the main game. In the Mercenaries game, they were much worse. Kill about a dozen Ganados, here they come.
WREE-WREE-WREE-WREE-WREE YEEEEEEAAAAARRRR!