Monster of the Day: Cell

Source:  Dragonball Z
Location:  Earth
Threat Assessment:  9.  In his own words:  "Like Piccolo I can fully regenerate as long as my core remains. Like the Saiyans my power increases greatly after I heal from near death, and like Frieza I can survive anywhere."  Add super strength, flight, the ability to absorb people for their power.  This Android is a constantly evolving nightmare.
Limitation:  None really.