Nothing certifies the greatness of a warrior in the Star Wars universe as the defeat of a Force-user. No one has hurt the Order more than the Sith and the names of the individuals that have taken the most number of Jedi lives will always live in infamy across the galaxy.
The most accomplished Knight killers have altered the course of the conflict between the Republic and the dark-side users and has made invaluable contributions to the Sith cause. Here are the 10 greatest Jedi killers of all time, ranked by the number of kills they have achieved from lowest to highest.
10 Darth Bane - At least 2
The creator of the Rule of Two was a former Jedi who betrayed the Order not just by devoting himself to the dark side. Darth Bane and his apprentice Darth Zannah became high-level targets of the Knights.
The Jedi's mission to eliminate them failed following a battle on Tython, where the Master and the Student were outnumbered but ended up being victorious. Bane slew 2 Jedi during that fateful confrontation.
9 Darth Traya - At least 3
The oldest and wisest member of the Sith Triumvirate and the master of Darth Sion and Darth Nihilus single-handedly killed a number of Jedi - Zez-Kal Ell, Vrook Lamar, and Kavar by cutting them off from the Force and then easily finishing them off.
The female Sith was also responsible for the planning of the First Jedi Purge, which resulted in numerous fatalities of members of the Order.
8 Savage Opress - At least 3
Darth Maul's brother was one of the main threats, which the Jedi Order had to deal with during the Clone Wars. The Zabrak used his ferocious will and undeniable skills to kill three Jedi Knights - Halsey, Knox, and Adi Galia.
Opress underwent a transformation which boosted both his physical and mental capabilities. Like Maul, he relied on a double-bladed lightsaber to beat his enemies into submission.
7 Aurra Sing - 4
Aurra was a powerful Force-user who left the Order and ended up turning into one of the most notorious Jedi killers during the Clone Wars. Her potent skills allowed her to end the lives of Sharad Hett, Peerce, J'Mikel, and Mana Veridi.
Through the Force, Sing could employ deadly telekinesis and be capable of enhanced jumps and reflexes that made her fast enough to evade the blaster bolts of droideka destroyers. Another skill that made the assassin quite lethal was her lightsaber mastery.
6 Darth Sidious - 4
The mastermind who created the Galactic Empire from the Skywalker saga was feared because of his ability to work behind the scenes. Nonetheless, Darth Sidious has personally taken out his fair share of Jedi, namely the team that was sent to arrest him, led by Mace Windu that consisted of Knights Kit Fisto, Saesee Tin, and Agen Kolar.
He is also practically responsible for all the Order 66 victims too but in that case, other soldiers did the dirty work for him.
5 General Grievous - At least 6
General Grievous was Count Dooku's greatest apprentice and his fighting skills at the Droid General's prime was best shown in Genndy Tartakovsky's Clone Wars animated show. He participates in two major battles in it - on Hypori and Coruscant, slaying 6 Jedi in the process.
Grievous inflicted additional damage to the Order through his involvement in various other confrontations throughout the Clone Wars, famously gathering a glorious collection of lightsabers through his military exploits.
4 Darth Sion - Dozens
Darth Sion's ravaged appearance didn't undermine his power. The student of Traya was responsible for many Jedi deaths, the exact number of which remains unknown. After he and Nihilus betrayed their master, they went on a Jedi killing spree, in which Sion was personally involved.
Although he suffered heavy wounds throughout the battles that followed, he added many successful battles against Knights to his resume. The campaign he led almost resulted in the total extinction of the Order and the Council.
3 Darth Malgus - Dozens
Malgus was a threat to be reckoned with during two major wars. The toughest blow that he dealt with the Jedi Order is depicted in the cinematic of Star Wars: The Old Republic "Deceived", in which he attacked the Jedi Temple on Coruscant.
Not only did he cut down a great number of Jedi, Masters, and Padawans during the battle but more notably, he overpowered and defeated Ven Zallow. Half of the Council's Jedi were killed following the surprise strike.
2 Darth Nihilus - Nearly 100
Arguably, the most powerful of the Sith Triumvirate, Darth Nihilus put to good use his immense life-draining powers and played his part well alongside Darth Sion during the First Jedi Purge. The Conclave of Katarr was the assembly point for many Jedi, who underestimated the power of Nihilus.
When he consumed the life of the entire planet, almost all the 100 Jedi that were gathered there lost their lives.
1 Darth Vader - Hundreds
The Sith that was given the honor of attacking the Jedi Temple exactly after the announcement of Order 66 was Darth Vader and he made full use of that golden opportunity. Every Jedi within the Temple was killed and one can only speculate as to just how many were killed by the 501st Legion and how many were killed by Anakin himself (possibly hundreds).
During his time as Darth Vader, the powerful Force-user continued to hunt down Jedi, devoting himself to the Order's extinction until he became aware of his son's existence.