Kylo Ren might have the coolest lightsaber in Star Wars, as its unstable nature due to its cracked kyber crystal makes the ‘saber look like a flaming sword as opposed to a beam of light, and the lateral vents give the appearance of an energy crossguard. No matter one’s opinion on Kylo Ren as a character or the sequel trilogy as a whole, this lightsaber is badass. But, perhaps it’s not the greatest, as that honor arguably goes to another Star Wars villain: a Sith called Darth Momin.

https://screenrant.com/star-wars-darth-momin-sith-lightsaber-op-ed/