Banzai Bills (マグナムキラー) are recurring enemies in the Mario series. They are an extremely large variety of Bullet Bills that first appeared in Super Mario World. Although they seem difficult to defeat, they can be defeated simply by jumping on them.
In Super Smash Flash 2
In Super Smash Flash 2, Banzai Bill is a hazard in Princess Peach's Castle. It may come flying toward the castle from any side of the stage, inflicting damage on contact. Once it reaches its destination, it plunges onto the castle, creating a large explosion. If a character gets caught in the explosion, the character will receive massive damage and will be KO'ed without a way to recover. However, Banzai Bill can be easily avoided.