If we're talking about general fiction, Hurin comes to mind. The battle and war having been lost, the army of Dor-Lomin, led by Hurin and Huor, cover the retreat of Turgon's army of Gondolin. They retreat until their backs are to the Sirion, then they retreat no more, but fight and die where they stand. They all fall, Tuor with an arrow in his eye, until only Hurin remains, crying "Day shall come again!" with each kill he makes, killing troll after troll that came at him. Morgoth decides he should be taken alive, so Gothmog's orc guard grapple with him, leaving their hands clinging to him even as he chopped their arms off, until he was eventually borne down by their weight.
For a historical example, the battle of Stamford Bridge, where Harold Godwinson surprised Harald Hardrada's army as they were relaxing. A single Norse warrior held the bridge against all comers, gaining time for Hardrada's men to get into their armour and prepare for battle. Unbeaten face to face, he eventually fell when a Saxon floated under the bridge on a piece of wood and thrust a spear into him from below.