These kinds of larger-than-life heroes are everywhere in medieval literature. You see them in Beowulf and other Anglo-Saxon epic poetry (like the Battle of Maldon), Gregory of Tours, the Icelandic Sagas, Arthurian romance, etc. Super-human heroes were as much a part of the medieval imagination as they are of our own re-imagining of the middle ages. So whether or not real people actually managed to live up to these heroic ideals, being the kind of badass who could hold off an army single-handed was definitely something to which real warriors aspired throughout the medieval period.

Figuring out if real people managed to reach this level of badassery is more difficult, because the lines between factual reporting and literary embellishment that matter so much in modern journalistic writing weren't as much of a priority in the middle ages. So while we have many historical accounts of people heroically and single-handedly fighting off multiple opponents, it's hard to tell if this is a real thing that happened, or the author remembering real events through the lens of tropes taken from epic literature and fiction.

But fiction and real life are always mutually structuring (fiction mirrors real life, and people model their actions on fictional ideals), so it's pretty safe to say that real people did sometimes pull off the kinds of heroic deeds that litter medieval literature (and that modern fantasy authors have taken up and worked into their stories).

The only one who comes to mind right now is Miyamoto Musashi, a Japanese swordsman who lived in the late 1500s and the first half of the 1600s. He was a soldier at the Battle of Sekigahara among others, but he also fought a great number of duels and was allegedly never defeated.

Ex: Jaime Lannister in Game of Thrones, Aragorn in Lord of the Rings, William Wallace in Braveheart, etc. (I know some of these are from different periods, or fantasy, but I think the premise remains the same.)