The point of balance* of a sword is just above the guard** of the hilt, the balance point is on the lower section of the blade. The balance point of an ax/hatchet is just below the head*** on the shaft. If all of the weight was in the handle of a sword, such that the hilt was much heavier, with the balance point precisely on the guard, how would that affect the usability of the sword? Too unweildly?
** Gaurd - a rounded knob on the end of the handle of a sword or dagger. (picture).
I got the idea for this question from this video. (It starts at that specific point).
You lose force in the slashing stroke and arguably a bit of fluidity. If all the weight is at the hilt you are pushing and pulling the blade everywhere, rather than having the weight of the weapon assist your movement. It will theoretically be quicker pulling back on defense, but slower and will lack force on offense when cutting ( same idea as the comparison in the video between and sword and axe ). A thrusting sword like a gladius will usually have the weight further back as you are using the weight of your body to help supply the force, a slashing weapon like a cavalry saber will generally have the balance forward a bit to lend force to cutting motions. A compromise between the two, like the straight sword in the video, will have the balance between those two extremes.
I’ll just add that it’s easier to control the tip in a sword more weighted towards the hilt, which is desirable in a thrusting weapon. Try it for yourself to see the difference. Get a wooden dowel or something and tape some weights on end. You can see that when the weight is on the pommel end, its a lot easier to rotate, while when the weight is on the tip, you get a lot more power in a cutting stroke.
Fencing weapons - sporting epees and foils, and historically, rapiers and smallswords - are heavily weighted toward the hilt for the reasons Enilno and Tamerlane point to: they’re for thrusting. With thrusting weapons, you don’t need a lot of power because it’s much easier to pierce flesh, clothing or armor with a point rather than an edge.
… but you need precision, because while piercing flesh is easy there’s a lot of space on the human body that can be poked at without causing too much immediate damage, or at least not enough to stop the other guy from poking at you right just this second. Hearts, eyes and necks are rather small targets, all things considered.
