Consider the scythe, and it's importance in mythology (i.e, the Grim Reaper) and its usage in anime. However, it does not seem to be very effective in real life. Is there any way to make the scythe more dangerous ? (adding poison is allowed)
The scythe is a tool designed for cutting at nearly ground level. Not ideal if you want to be cutting about 5 foot up.
The first thing you're going to do is straighten the blade relative to the handle, maybe even face it entirely in line with the handle rather than at 90deg.
At this point you realise you've started with entirely the wrong tool as what you've just created is better known as a billhook (they come with long and short handles) which is basically a polearm with a civilian name.
As you can see from the above image, the billhook, unlike the scythe, is very much still in use to this day. It's far easier to use and is much more versatile.