A unique ability possessed by Mace Windu could have prevented the Clone Wars from happening in the Star Wars galaxy. A senior member of the High Council, Mace Windu (best known by Samuel L. Jackson's interpretation) was one of the most powerful Jedi Masters during the prequel era of films, a brutally effective warrior wielding his iconic purple lightsaber. However, Mace also carried a rare Force power that could have changed the entire trajectory of the galaxy had he acted differently during Attack of the Clones.
In Matt Stover's now non-canonical novel Shatterpoint, it was revealed that Mace Windu was well-versed in battle meditation with the ability to sense shatterpoints through the Force. A rare skill that did eventually make its way to the canon, Mace can sense the greatest point of vulnerability in any object, opponent, or event, giving him a keen advantage during conflicts. As such, the novel confirms that Mace saw Count Dooku as the shatterpoint of Star Wars' Clone Wars, a concept that was likely true in the established canon as well.
Dooku's Death Would Have Ended The Clone Wars
Despite identifying Dooku as the Clone Wars' shatterpoint in the novel, Mace prioritized saving Anakin Skywalker and Obi-Wan Kenobi in Attack of the Clones, even though killing Dooku would have likely prevented the war. This was probably because Mace similarly saw Anakin as the shatterpoint for several different future events, a determination that made sense given Skywalker's status as the prophesied Chosen One. Canonically, it still makes sense that Dooku was the Clone Wars' shatterpoint. He was extremely important to the Separatist movement as their chief leader and the one responsible for rallying the various systems that were no longer content with the state of the Galactic Republic.
Killing off Dooku in Star Wars would have gone a long way in preventing the Clone Wars from progressing as it did, and it might have ended the widespread conflict entirely. As such, one can only imagine how the galaxy would have turned out had Mace slain Dooku during the Clone Wars' very first battle on Geonosis. Interestingly enough, Windu and Jedi Council did eventually assign Quinlan Vos with a mission to assassinate Dooku in the Star Wars canon (though he was naturally unsuccessful).
The Galaxy Would Have Remained On The Brink Of War
While the Clone Wars would have likely ended with Dooku's death, that doesn't necessarily mean the conflict between the Republic and Separatist Alliance would have instantly stopped. There was far too much tension and opposing politics present that the galaxy would have still been on the edge of civil war. However, it stands to reason that Star Wars' Republic and its new army would have been able to capitalize on the momentum gained had Mace Windu eliminated the leader of the Separatist movement. The lack of leadership and resulting power vacuum would have allowed the Republic to maintain the peace while negotiations and conditions for surrender potentially took place.
Could Palpatine Have Engineered The Clone Wars Without Dooku?
Another factor worth exploring is whether Palpatine would have been able to keep his machinations going without Dooku. Had Windu indeed killed the Count, Darth Sidious would have lost his apprentice whom he'd installed as the Separatist leader while he continued to play the part of Chancellor, manipulating the war from both sides. While one could argue that Palpatine could've had General Grievous assume command, as seen in Revenge of the Sith, it's unlikely Grievous would have been able to maintain the Separatist Alliance as well as Dooku did long-term while also serving the higher purpose of Palpatine.
Without Count Dooku, Palpatine would have had to massively accelerate his plans with an even greater level of risk. Alternatively, he might have needed a completely different scheme entirely. At any rate, Mace Windu could have changed the entire course of the Clone Wars by taking out Dooku, though his decision to rescue his fellow Jedi shows his heroism and loyalty. Although Mace Windu's ability was likely diminished by the Sith's shroud of darkness that kept the Jedi from foreseeing the future during this era, it makes perfect sense that he could still see Dooku as a crucial shatterpoint in the massive conflict that took over the Star Wars galaxy.