Through the Force, Yoda was considered to have mastered Form IV to its highest level. He used it in almost all of his battles, and his mastery of the style caused others to describe him as virtually unstoppable against most opponents, including Separatist battle droids, despite his small size and advanced age.
An example of a Jedi swordmaster was Mace Windu, considered as such because he was a master of all forms of lightsaber combat and due to his mastery of Vaapad, which he created.
Jedi Masters Vrook Lamar, Zez-Kai Ell, and Kavar were all skilled in its use and were able to pass on their experience to others. Jedi Master Atris, who fell to the dark side during the First Jedi Purge, was also known to employ the form.
Yoda certainly knew all the lightsaber forms. Partially because he taught them (or at the very least Shii-Cho, Form 1) to younglings. He was also likely proficient in all the forms and knew the techniques. However, he heavily preferred Ataru, the fourth form.
It could be used to combine double-bladed lightsaber combat with other Force abilities, like pushes and lifts. Darth Maul had mastered this form and employed it in his duel against Obi-Wan Kenobi in the Theed power generator.
After turning to the dark side and joining the Sith, Vader continued to employ Form V. His secret apprentice, Galen Marek, was also familiar with the form, having been personally trained in its usage by Vader.
Kylo Ren's Lightsaber Form
The evidence isn't entirely clear, but it is most likely that he was an adherent of Form V, particularly the Djem So variant. Ren's fierce fighting style has the hallmarks of Djem So, which demands a high degree of speed and strength to execute a flurry of attacks and counterattacks.
The oldest of the seven lightsaber forms, as well as the most basic, is Shii-Cho form, otherwise known as The Way of the Sarlacc and The Determination Form. Shii-Cho is traditionally the first lightsaber form taught to Jedi initiates.
Obi-Wan Kenobi was highly skilled in Form III.
Notable practitioners
In more recent years, the form was mastered by the Jedi swordmaster Cin Drallig along with the other six forms. Grand Master Yoda and Swordmaster Mace Windu were also proficient in its usage, as they were said to have fully mastered all the seven forms of lightsaber combat.
Form I, also known as Shii-Cho, The Way of the Sarlacc, or The Determination Form, was the oldest and most rudimentary form of lightsaber combat developed by the Jedi Order and was taught to all members of the Jedi Order.
Sokan was a form of lightsaber combat. Developed by the ancient Jedi Knights during the Great Sith War, Sokan combined tactics that allowed for evasion and mobility with the kinetic motions of Form V combat.
There are 7 forms of lightsaber combat, but Soreso, Shein, and Vaapad are the most effective. Soreso, Vaapad, Shein, are the most effective forms because they are all strategic and have their strengths and weaknesses.
Anakin Skywalker was very skilled at Djem So and showcased his mastery over the form during the Clone Wars. His Padawan, Ahsoka Tano, was also known to favor Form V. Form V was a physically demanding style, calling on the user to quickly transition from a dedicated defensive stance to an all-out attack.
Mace Windu, with his lightsaber combat form Vaapad, could reflect the lightning back to its source with a "superconducting loop". It required tremendous effort on the reflector's part, however, as seen in Windu's battle with Palpatine; Windu was seemingly able to overcome Palpatine's lightning.
The Forbidden Forms were forms of lightsaber combat used by the Sith during the Sith Wars. According to the testimonies of the Jedi Cervil the Uncanny, lightwhips—a lightsaber variant with a flexible blade—were used to defend against Sith Lords who utilized the forms.
Form VII: Juyo (or Vaapad)
Form VII is the last known form of lightsaber combat and is known to be the most aggressive. Jedi Master Mace windu is the main Jedi known to use this form of combat because Form VII is the most aggressive and only the most Force-sensitive individuals can execute this form successfully.
There were seven known forms of lightsaber combat: Form I, Form II, Form III, Form IV, Form V, Form VI, and Form VII.
1. Mace Windu. One of two Jedi responsible for creating a new fighting style known as Vaapad, Mace Windu mastered the most difficult form of lightsaber dueling.
This isn't to say that Mace Windu isn't powerful when it comes to the force. He's on par with Darth Maul and is more powerful than Qui-Gon Jinn. But, Obi-Wan is still the stronger Force user which makes him a powerful combatant.
Mace specialized in the seventh form of lightsaber combat, AKA Juyo or Vaapad. Windu was the only known practitioner of this form that didn't fall to the Dark Side, mainly because the style calls for an aggressive, unpredictable approach (much like Maul's, just less jumping around).
Given that she studied Luke's ancient Jedi texts and was trained by Leia, Rey most likely used a variation of Form VI, Niman. Form VI, Niman, takes elements from the previous five forms and combines them into a pastiche that's proficient in all situations, but lacks the specialization of other forms.
Qui-Gon Jinn was known for using Ataru, the same form that Yoda used. This form was known for the intense acrobatics that were involved, with this one having the most complex maneuvers out of all of the forms.