Obi-Wan's Weakness Stemmed From Lost Hope and Purpose They match the way he rediscovers his hope and his purpose, most notably in his efforts to rescue Princess Leia. Leia herself is a potent Force user, though her abilities are far more subtle than those of her kin.
In addition to getting older, Obi-Wan's life as a whole has slowed down considerably. He hasn't been using the Force, nor has he been training padawans or saving the galaxy from the Sith. With these things in mind, it makes sense for Obi-Wan to be rather weak in his new Star Wars show.
Powers and Abilities
The Force: Kenobi was extremely powerful, and had an extremely strong connection to the Force, and was one of the most powerful force users of his time. Though Kenobi did focus largely on Lightsaber combat, he was also very skilled and powerful in use of the Force.
In order to hide from the Empire, he needed to keep a low profile. This means that he's not in his best fighting form. Couple that with his wavering faith and he isn't really attuned with the Force, further impeding his fighting skills.
However, his arrogance in believing that he would be able to overthrow Palpatine ended up being his greatest downfall. In his anger, he attacked Padme and took on Obi-Wan in a duel to the death, which ultimately left him crippled for the rest of his life.
Anakin admits to Obi-Wan that he has been arrogant and unappreciative of his training, and apologizes to his master. Obi-Wan assures Anakin that he is proud of him, telling him that he has become a "far greater Jedi than I could ever hope to be."
Vader responded “I am not your failure, Obi-Wan. You didn't kill Anakin Skywalker. I did.” This allows Obi-Wan to finally accept that Anakin is truly gone and that there was nothing he could have realistically done to save him.
Master Yoda has risen above all others to claim the top spot as the most powerful Jedi of all time and the true chosen one according to IGN's audience. He won pretty handily as well, as he was victorious in 89,756 of his 95,243 battles and had a win percentage of 94.2%.
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.
Darth Sidious was always stronger than Vader, which is why he ruled over him for almost 20 years and turned him into the Sith Lord he was.
#1 – Yoda. Yoda is widely considered to be the greatest Jedi of all time, and with good reason. He is a master of the Force, a skilled warrior, and has an unmatched wisdom that comes from centuries of experience. He is the embodiment of what it means to be a Jedi, and his legacy lives on long after his death.
Between Darth Vader and Obi-Wan, it's pretty clear that Vader is far more powerful with the force. After all, he pretty easily used the force to stop a starship from taking off in the previous episode, and manhandled Kenobi throughout the majority of the show.
In his prime, he was able to defeat numerous powerful adversaries such as Darth Maul, General Grievous, as well as a pre-cyborg Darth Vader. While he was mainly known as the master of the third form of traditional lightsaber combat, Soresu wasn't the only one of the seven forms Obi-Wan would employ on-screen.
The main reason for this is due to Kenobi's long stint in hiding. Again, Kenobi has been in hiding for around ten years, slowly diminishing his connection to the Force. While the Force, and people's abilities with it, are hard to define in Star Wars, it remains the case that the Force acts as any other skill does.
Obi-Wan knew it was only a matter of time. So, he made the difficult decision to use his learnings and become one with the force, rather than let Vader decapitate him.
So instead of risking letting his emotions get the better of him, Darth Vader opts to let Obi-Wan go with the assumption that he is no threat to him or the Empire.
Obi Wan is one of the most powerful Jedi to have ever lived. He is the best defensive duelist in galactic history according to Mace Windu and numerous factbooks. He had a low sensitivity to the force but mastered it to his fullest potential worshiping the force as opposed to bending it to his will.
Darth Sidious / Emperor Palpatine
Darth Sidious was one of the destructive maniacal Sith lords and the most powerful character in Star Wars. He caused the fall of the Galactic Republic and the Jedi Order, using his two personas through which he was able to manipulate most events in the galaxy.
Unwilling to see his son die, Vader gave his life to save Luke, thereby dying as Anakin Skywalker. Anakin ultimately fulfilled his role as the Chosen One and brought balance to the Force, fulfilling Qui-Gon Jinn's belief in the prophecy that foretold Anakin's destiny.
Biography. Legend had it that Yoda—a Jedi who became Grand Master—was trained by N'Kata Del Gormo.
1 Darth Sidious
There has been no Sith, as powerful, meticulous, nor as evil as the Emperor himself, Darth Sidious. As previously mentioned, Sidious trained in the Dark Side by Darth Plagueis before Sidious killed Plagueis in his sleep, making Sidious a Sith Master.
He slays Sidious and returns to Obi-Wan, begging for atonement by execution, only to be met with true forgiveness instead. But just as this fantasy Obi-Wan refuses to strike his former friend down, Vader refuses to turn his back on the dark.
He does. Right at the end. With Luke crying over him and Vader sensing his anguish and pain he had inflicted on all those who had cared for him.
It mostly stemmed from Anakin feeling that he was shown disrespect by the Jedi High Council when it wouldn't promote or trust him as much as he believed they should. This condescension is something Anakin often voiced to Padme Amidala, who would oftentimes offer him consolation.