When it comes to weaponry in the Star Wars universe, the lightsaber is perhaps the most prominent. In addition to different colors and designs, certain lightsabers have more power than others. Star Wars: Rebels Season 1, Episode 10, "Path of the Jedi," revealed a lightsaber blaster for the first time. Belonging to Ezra Bridger, this weapon marked a major upgrade -- and later, Master Jocasta Nu revealed a lightsaber rifle in Star Wars: Darth Vader #9, which was even more powerful.
Not only did this provide a completely new use and format for the traditional Jedi weapon, it brought to bear just how powerful they could be. In fact, the weapon reached critical capacity after firing five massive blasts during Master Nu's battle with Darth Vader in the Jedi Archives.
Those five blasts alone are enough to melt down Master Nu's saber, which was powering the rifle. In Star Wars: Darth Vader #9, she loads her lightsaber into a slot at the top of the fancy firearm. After five shots, the depleted and destroyed saber pops out. Then she hurls her overloaded weapon at Darth Vader with the Force. The lightsaber rifle explodes, inflicting a huge amount of damage on the Jedi Archives. Even depleted, the weapon is incredibly dangerous.
A lightsaber has always been both offensive and defensive, extremely powerful and reputedly very hard to use, which is why they are really only used by Jedi, Sith and other Force-sensitive beings. They were designed for close-quarter combat and, ultimately, are considered an honorable weapon.
In comparison, while the lightsaber rifle is clearly powerful and dangerous (so much so it was hidden away in the Jedi Archives), Ezra's lightsaber blaster is viewed more generously. "Well, it's different... but that seems about right for you," Jedi Kanan Jarrus says in Star Wars: Rebels Season 1, Episode 10. In this case, Ezra's lightsaber is a prototype built based on his experience level. Still learning the ways of the Force and the intricacies of wielding a lightsaber, Ezra adds a non-lethal, primarily defensive stun-burst capability to his lightsaber design.
The ethical implications of creating a kyber crystal-powered distance weapon are more clearly outlined in Marvel's Star Wars: Doctor Aphra #32. The issue opens with a flashback, featuring Doctor Aphra's father and a young Chelli Lona Aphra herself. Her father has come across a "repository of Jedi Heresiologies," featuring Jedi Renegade Oo'ob the Apostate. Oo'ob is pictured holding a sniper rifle.
Years later, Doctor Aphra finds the weapon in question: The Farkiller. "A magnification attenuator," she explains. "Lightsaber tech used in a sniper rifle ... Oo'ob could take out targets from over 100 klicks away. He was excommunicated for it!"
It's not only the power of the weapon, but the implications of its use, that reportedly lead to Oo'ob's excommunication. He supposedly broke Jedi doctrine to "pursue a pre-emptive approach to threats," in turn recruiting Jedi crystallist Var-Hill to modify lightsaber technology and create the Farkiller, a weapon he used to assassinate potential threats.
Ultimately, while the lightsaber rifle was likely created and designed with the best intentions, the Jedi powers-that-be determined the sheer power and danger of it required safeguarding and locked it away in the Jedi Archives. A lightsaber on its own, even when wielded by Sith, doesn't represent power and destructiveness. In the words of Obi Wan himself, "This is the weapon of a Jedi Knight. Not as clumsy or random as a blaster; an elegant weapon for a more civilized age."