Does the naming of Khalid ibn al-Walid as "the Drawn Sword of God" mean that he is infallible, despite the Prophet's (peace and blessings be upon him) saying: "O Allah, I disavow before You what Khalid has done"?

There is no contradiction between the Prophet's (peace be upon him) description of Khalid ibn al-Walid as "a sword from the swords of Allah" and his statement: "O Allah, I disavow before You what Khalid has done." The first description refers to his severity against enemies and his effectiveness in dealing with them, not his infallibility from error. As for the second, it was due to an erroneous interpretation by Khalid, who misunderstood the statement of Banu Jadhimah, "Sabā'nā" (we have apostatized/converted), to mean disbelief rather than embracing Islam. The Prophet disavowed this action of his due to his lack of verification, yet he did not dismiss him, which indicates that the error was a matter of interpretation and ijtihad, not intentional wrongdoing.