Let the lightsaber be a lightsaber.
Instead of trying to make something that out-performs a lightsaber at being a lightsaber, make something that does what a lightsaber can't.
I would say that a sword is a sword is a sword. But here, on this site, only a sword that can parry and clash with a lightsaber is a real sword. Beyond that, it's not cutting power that you want. What you want is utility. A lightsaber is as much of a tool as it is a weapon. You can cut through bulkhead doors with it. You can even use it to light your cigarette.
Want a sword that can cut through walls? Put a Force Pike or plasma torch in the hilt or at the tip.
Want to give a FU nasty surprise? Line the blade with Cortosis or Ionite to fry their fancy lightsaber.
Hire an alchemist to treat your sword to catch lighting.
Maybe get it treated with a leather or bone handle... get it to trigger on emotion, not focus or concentration (every living thing is connected to the Force, not just Jedi)... Give it some neat alchemical ability like overloading the adrenal system of anyone holding it, making them feel as if time is slowing down when they get angry. Or maybe go Full Metal Alchemist and get the alchemy in the blade to cause rapid oxidization of any metal that comes into contact with the blade (aka, a sword that makes stuff rust).
There are a lot of cool things that can be done if you decide to put the time and effort into it. Stuff that goes well beyond the capabilities of a lightsaber.
Just... Let the freaking lightsaber be a lightsaber.