Who was the strongest Companion in combat?

The Prophet (peace be upon him) raised his companions to be patient, to strive [in the way of Allah], and to be strong in upholding the truth. Thus, they were courageous and mighty in defending the truth, examples of whom include: Ali ibn Abi Talib, Sa'd ibn Abi Waqqas, Al-Zubayr ibn Al-Awwam, Umar ibn Al-Khattab, Khalid ibn Al-Walid, Ubadah ibn Al-Samit, Sa'd ibn Ubadah, Abu Dujanah, Al-Qa'qa' ibn Amr Al-Tamimi, and Al-Muthanna ibn Harithah Al-Shaybani. Some of them were considered to be equivalent to a thousand men, such as Al-Zubayr ibn Al-Awwam, Ubadah ibn Al-Samit, Al-Miqdad ibn Al-Aswad, and Maslamah ibn Mukhallad. Umar said of Al-Qa'qa' ibn Amr, "An army that includes him will never be defeated." And Abu Bakr said of him, "His voice in the army is better than a thousand men." You can find details of their strength and bravery in books of biography, history, and notable figures.