One of the greatest tragedies in Star Wars lore is the death of Jedi Master Qui-Gon Jinn. For a character with just one movie (and a few episodes of The Clone Wars) worth of screentime, Qui-Gon had one of the most underappreciated impacts on the entire Star Wars universe.
Darth Maul's slaying of Qui-Gon Jinn essentially opened the door for most of the events of the prequel trilogy (and the subsequent trilogies that followed) to unfold. Had the decision been made to have him survive the Duel of the Fates, we could be looking at a significantly different Star Wars story. From the events of the films and other canonical materials themselves to the paths of certain characters, Quin-Gon Jinn's death arguably shaped the entire course of the Star Wars universe.
10 Darth Maul's Fate
The Duel of the Fates saw Qui-Gon's demise come at the hands of the maniacal Sith Lord Darth Maul, eventually opening the door for his padawan, Obi-Wan Kenobi, to strike down his master's killer. Or so we all thought.
As we've learned from the events of The Clone Wars, Rebels, and even Solo: A Star Wars Story, Maul survived his duel with Obi-Wan, leaving him to terrorize the galaxy on his quest to seek revenge on Kenobi. Qui-Gon's death essentially initiated the course for a more in-depth Maul story that expanded far beyond the events of The Phantom Menace. If Qui-Gon had survived their battle, it can only be assumed that he and Obi-Wan would've properly killed Maul and forced such an incredible villain to be just a one-movie character.
9 Count Dooku's Fate
Darth Maul isn't the only Sith Lord whose life dramatically felt the impact of Qui-Gon's death. The other? None other than his former master, Count Dooku. For years fans have theorized that through the events of The Phantom Menace, Dooku was groomed by Palpatine to turn to the Sith and set in motion the creation of the clone army. At this point in the timeline, however, he's still technically part of the Jedi Order.
So, if his former apprentice had survived his duel with Maul, would Dooku's path and fate still be the same? Many believe that Qui-Gon could've been the voice of reason for Dooku that deterred him from joining the Sith. It's not far-fetched to believe that Qui-Gon could've helped keep Dooku on the side of the Jedi, avoiding Palpatine's betrayal and the gruesome end he met in Revenge of the Sith.
8 The Ideologies of the Jedi Council
One of the more well-known aspects of Qui-Gon's character, and more importantly his role among the Jedi, was his connection and understanding of the force. He always allowed the force to guide his actions and steer him clear of the politics of the Republic. It's not only what helped him discover the chosen one, Anakin Skywalker, but also what kept him off of the Jedi Council.
It was clear Qui-Gon operated by his own code, separate from those of the Jedi Order and fellow masters like Yoda and Mace Windu, and that he saw a dangerous course for the Jedi. Throughout the events of Attack of the Clones and Revenge of the Sith, the ideologies and methods of the Jedi Council were unmovable, allowing the Sith to thrive right beneath their noses. Nearly no one, with the exception of Anakin Skywalker, ever questioned the Jedi Council, and that ultimately led to the fall of their order. Although some believe that Qui-Gon would've eventually left the order, he still could've been the one defying voice that could've beneficially altered the dogmatic views of the other Jedi and prevented their catastrophic fall.
7 The Relationships of His Padawans
Qui-Gon's understanding of both the light and dark elements of the force also allowed him to recognize the importance of interpersonal connection, even of a Jedi. As was made painfully clear throughout the prequels and much of The Clone Wars, the Jedi had fairly strict principles about romance and relationships among their order.
As an unfortunate and obvious result of those principles, both of Qui-Gon's padawans (if you're willing to assume that Anakin would've become his padawan) were forced to suppress and/or hide their true feelings. Obi-Wan completely avoided and concealed his feelings for the Mandalorian dutchess Satine while Anakin chose to carry out, but carefully hide, his relationship with Padmé Amidala. Having experienced similar feelings back in his earlier years with a fellow Jedi known as Tahl, Qui-Gon could've taught his padawans that they were not worth repressing out of fear of the Jedi finding out. For all we know, his teachings could've helped Obi-Wan and Anakin save the lives of both Satine and Padmé.
6 Obi-Wan's Role in it All
It's no secret that one of the most obvious impacts Qui-Gon's death had on the Star Wars universe was forcing Obi-Wan to assume the role of Anakin Skywalker's Jedi master. In fact, his death elevated Obi-Wan's role in the story entirely, leading him to become one of the most important Jedi in history.
The untimely and unexpected loss of his master forced Obi-Wan to assume the role of Jedi master with most of his training under Qui-Gon assumingly incomplete. It's what ultimately led him to fall in line with the principles of the Jedi Order, and become an unquestioning soldier in the eventual war. Had Qui-Gon Jinn survived, Obi-Wan would've never shared the relationship with Anakin that led to the events of the prequels and while he would've likely still been a significant figure in the Star Wars universe, he would've never taken on the role that he did.
5 The Course of the Clone Wars
One of the greatest speculative theories about Qui-Gon Jinn is how he would've folded into the events of the Clone Wars. One half of that theory questions whether Qui-Gon would've assumed the role of a Jedi soldier fighting on behalf of the Republic like Obi-Wan and Anakin or as an advisor throughout the war similar to Yoda and Mace Windu.
The other part of the theory wonders if he would've been able to sense the truth behind the Clone Wars that so many Jedi managed to overlook. There's no guarantee that Qui-Gon would've been able to spot the truth behind the clones and the subsequent war, but considering his understanding of both sides of the force, he likely had a better chance at uncovering the Emperor's plot than any other Jedi.
4 Palpatine's Path
Qui-Gon Jinn clearly represented the father figure that Anakin Skywalker needed in his life. After his death, Obi-Wan did his best to assume that role but clearly became more a brotherly figure than a father.
Obviously, that left one person for Anakin to seek fatherly mentorship from in the absence of Qui-Gon: Chancellor Palpatine. Qui Gon's death basically opened the door for Palpatine to groom Anakin to eventually become Darth Vader, with the rest of the Jedi unable and unwilling to search the depths of the dark side to uncover this scheme.
3 Detection of the Sith
There was obvious merit in Qui-Gon's willingness to understand both the light and dark sides of the force. It not only elevated his understanding of the force itself, but it allowed him to see through the curtain cast across that Jedi that led them to miss the painfully obvious resurgence of the Sith.
Again, there are no guarantees, but it's hard to believe had Qui-Gon survived that he wouldn't have played a role in uncovering the truth of Chancellor Palpatine and his plans to overthrow the Republic. Had he made it through his duel with Maul, his force awareness would've likely led him right into the path and plans of Darth Sidious.
2 Further Discovery of the Force
By far one of the most notable impacts of Qui-Gon's death was the discovery of life after death via the force. At the end of Revenge of the Sith, Yoda alludes to Obi-Wan that his former master had discovered a way to exist even in the afterlife.
Fans of The Clone Wars know that Qui-Gon was responsible for teaching Yoda and Obi-Wan how to master this aspect of the force that we saw them utilize at the end of Return of the Jedi. It not only proved that, through the force, there was a sense of life even in death, but also that Qui-Gon was clearly one of the most powerful force-wielders the galaxy had ever seen.
1 Anakin's Turn
Arguably the most evident impact Qui-Gon's death had on the Star Wars universe was the turning of Anakin Skywalker. It's easy to assume that, had he survived, Qui-Gon would've taken the task of training Anakin, which would've likely deterred him from relying so heavily on Palpatine and eventually, the dark side.
It may feel strange to believe that such a small change as a different master would've completely altered the course of one of the universe's most important characters, but it's fairly widely agreed upon that if anyone could've had that impact on Anakin, it was Qui-Gon Jinn.