For me it comes down to two moments, one is medieval and one is sort of not really medieval but close enough.
First one is of Sir Thomas Holland. He was on campaign with Edward III when they took Caen. He took the Count of Eu and Guînes, Constable of France as his prisoner.
He surrendered to him, according to the chronicles of Jean Le Bel he shouted:
"Ah! In God's name, sir knights, come up here and save us from those pitiless men who'll kill us like all the others if they catch us!"
Sir Thomas and his men would secure their prisoners and once finished immediately rushed back to the fray to protect women and young girls from violence.
Caen was brutally sacked, but these women were honorably saved and protected because of the actions of Sir Thomas Holland.
Second one is after the 1512 siege of Brescia, the Chevalier Bayard was injured and taken to a nobles nearby residence where he recuperated.
He protected the nobleman’s wife and daughters from harm.
When he learned of the impending battle at Ravenna, Bayard prepared to leave, despite his injury, to rejoin his comrades.
As a gesture of gratitude, he gave the daughters a thousand gold ducats each, using the ransom money their mother had offered him for the family’s safety.
What do you think was the greatest moment of chivalry in the medieval age?