The Gladius Hispaniensis of the Roman Empire
Short, wide blade, very light, one-handed, very fast, impressive enough to nail as to cut, almost any wound caused by that blade was devastating, could dismember arms, legs and heads in one fell swoop, or completely traverse the enemy with a single stab, and all with one hand.
And why was it the best sword in history?
Because this sword gave victory in countless battles to the Roman Empire for 700 years. The combination of the Scutum (Roman shield) and the Gladius was lethal in battle. When an enemy army was launched on the legions collided with the huge Roman shields and without much space it was not possible to brandish spears, swords or long scimitars, however a gladius was maneuverable.
No weapon, neither white nor fire, has been as active and as successful as Gladius Hispaniensis. 7 centuries winning battles, 7 centuries being an object of military elite and also civil, since for its small size and lightness it was also easy to carry by Roman citizens, and it was also easy to hide under the togas.
Another of its advantages is that it allows the inverted grip, to take it as if it were a dagger, and it is still as deadly. This is not possible with medieval swords, scimitars or sabers. With katanas it is, but be careful, it is not so rigid the grip inverted in a katana and you have to be very trained to do it well.
By the way, the origin of Gladius is Iberian, hence its name; hispaniensis. The Romans "signed" the Hispanic smiths, the best of the empire, to make them. So technically the most deadly weapon in history, causing millions of deaths for 700 years, is a "Spanish" invention
If we had to look for a descendant of the Gladius Hispaniensis, I would say that his successor is the machete. It is not technically a weapon, it is rather a tool, but in case of combat its use would resemble a Gladius Hispaniensis very much. And honestly, I think that the majority, in case of opting for a defense weapon, would choose the machete before a katana.
