how well would a scythe work as a weapon?

Despite how cool TV and video games make scythes look, they're actually horrible as weapons. The only thing they can do is cut and pull; they can't thrust, they can't pierce, and they have very little mobility. Even in the hands of a master, a scythe can only do so much, that's why TV and video games always have some sort of gimmick to the wielders, like superpowers or technology, that make them usable.

If you want a weapon that's similar to a scythe, check out the dagger-axe, it's pretty much a scythe with a small blade, but unlike the scythe, the weapon's light blade allows for mobility and can pierce through armor. Also check out the halberd, which is usually a spear with a giant blade or an axe with a long pole.

A scythe is more of an Aesthetic weapon than anything. I'd recommend a rapier, or a mace as a weapon.

They are pretty much the same thing. Both have a horizontal blade, but their uses are to harvest different different things. A farming scythe harvests crops, a scythe weapon harvests souls.

Go Gundam death scythe

hhmmm..... not very well. You can't thrust, you have to pull with it. You could swipe at the right angle, but it would be awkward. Your enemy would have to be very close to actually do any damage and both your hands would be on the handle, so you'd be screwed.