Grievous
General Grievous was the military commander of the armies of the Confederacy of Independent Systems during the latter years of the Clone Wars.
Cyborg Body
General Grievous was a cyborg an organic brain and cardio-pulmonary system contained in a droid body. What illness or injury required this extreme treatment is unknown.
Grievous's droid body is physically stronger than that of a human being. He has four arm and two legs. The chest cavity containing his heart and lungs can be opened for servicing, and Obi-Wan Kenobi was able to force it open enough to attack Grievous' vital organs.
Lightsabre Combat
General Grievous collected lightsabres from defeated Jedi and occasionally used them in duels, having received training from Count Dooku in their use. While not able to manipulate the Force like a Jedi or Sith, Grievous's mechanical body enabled him wield up to four lightsabres and manipulate them in ways that were physically impossible for his humanoid opponents. With these advantages and his superhuman strength, Grievous could be a serious threat to a Jedi in lightsabre combat.
Military History
General Grievous was a ruthless military commander reputed to have ordered the depopulation of more than one Republic planet.