Grievous's droid body was physically stronger than that of a human being. He had four arms and two legs. The chest cavity containing his heart and lungs could be opened for servicing, and Obi-Wan Kenobi was able to force it open enough to attack Grievous' vital organs.
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 at once 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.