Qui Gon jinn's death affected many people in the order. However, it hit the hardest for Dooku, as he was his old master many years ago. that pretty much raised him as a boy. So when he heard what happened, he was immediately filled with sadness and anger, leading him to leave the Jedi Order.
When Qui-Gon was killed by Darth Maul, Dooku was so saddened that Qui-Gon's death lead to Dooku's transformation into the Sith Lord Darth Tyranus. He would later provoke the memory against Obi-Wan Kenobi, Jinn's apprentice.
You can also see how much Qui Gon Jinn's death affected Dooku when he was talking to Obi Wan in AOTC. Look at the raw, pure emotion Dooku feels over a decade after Qui-Gon died. It affected him significantly.
Jinn's former master, Count Dooku, had been considered to attend the funeral but had declined the invitation, claiming he would not be "pleasant company".
Count Dooku's Reaction to Qui Gon Jinn's Death - Star Wars Explained
Would Dooku have turned if Qui-Gon was alive?
Dooku, AND Anakin, would be less likely to fall to the dark side if Qui-Gon was left alive and Maul's sympathetic past would never be revealed. For the former, Order 66 wouldn't be executed since Dooku wouldn't be the one planning to do that on the clones.
Dooku is 69. 32 BBY: The events of The Phantom Menace (Qui-Gon's death by Maul), and Sifo-Dyas's death from the Pykes as ordered by Dooku (per Star Wars: The Clone Wars: Character Encyclopedia) in the same year. Dooku is 70.
Jinn had at least some contact with his old Master after taking on Kenobi and spoke highly of his Padawan to Dooku. However, Dooku left the Jedi Order after the invasion of Serenno, secretly becoming a Sith apprentice to the elusive Sith Lord Darth Sidious sometime later.
The two were able to free Maul after he had been interrogated by the Sith Lord Count Dooku, and together the three rendezvoused with more Death Watch forces on the moon of Zanbar. Maul took command of his forces once again, and assured them that the war they had longed for was at hand.
Obi-Wan is good at letting his emotions go. He feels them in the moment, the anger and sadness over deaths of ones he loved like Qui-Gon and Satine. The guilt and pain over Anakin's turn. He feels them deeply, and then lets them go.
Darth Sidious, was in the earliest stages of his plan to take over the galaxy, and he was afraid a certain Jedi might get in his way. Interestingly, however, that Jedi wasn't Yoda or Master Windu, but instead Qui-Gon Jinn.
With a potential Jedi Code-defying love affair with another Jedi, Dooku is more of a foil to his Clone Wars-era enemies, Anakin Skywalker and Obi-Wan Kenobi, with Dooku's lover, Jedi Master Jocasta Nu, possibly retaining feelings for Dooku well after he joined the ranks of the Lost Twenty.
Because Maul punched him with the hilt of his saber and then stabs him faster than Qui-Gon can pull back his blade. So Qui-Gon lost because Maul was physically stronger and quicker than him. Qui-Gon is skilled but not a prodigy. And he's quickly worn down by Maul in both their encounters.
Unfortunately, the Dark Side soon took hold of him. He murdered Yaddle and pledged himself to Darth Sidious. However, Yaddle wasn't the only Jedi that Dooku killed. Yoda #4 (by Jody Houser, Luke Ross, Nolan Woodard, and VC's Joe Caragagna) showed how Dooku brutally killed his biggest fan.
Sidious revealed to Maul that he did not intend to kill his former apprentice, as he still had use for Maul; it was Sidious' hope that Maul would lead the Sith to Mother Talzin, Maul's mother and the leader of the Nightsisters, so she could be eliminated as a potential threat to the eventual Sith rule of the galaxy.
Katri was a Mirialan Jedi Master and member of the Jedi Order's Jedi High Council. Between 68 BBY and 42 BBY, she was killed by a group of security guards on Raxus Secundus, and her death was investigated by Jedi Masters Mace Windu and Dooku.
In the Star Wars prequel trilogy, the Jedi Order learned that Count Dooku was a Sith Lord in the film "Star Wars: Episode II - Attack of the Clones." The revelation occurred during the course of the movie's events, which were set approximately ten years after the events of "Star Wars: Episode I - The Phantom Menace."
Although Qui-Gon never felt close with him, Dooku was quite fond of his former pupil, and Jinn's death on Naboo devastated him. The 2012 Legends novel Darth Plagueis showed Dooku's gradual fall to the dark side in detail, and his feelings on the death of Qui-Gon contributed to this fall from grace.
Count Dooku's real name, Dooku, was more fitting than his Sith title, Darth Tyranus, as it speaks to his manipulative nature. Dooku played a crucial role in weakening the Jedi and the Republic from within, planting doubt and eroding trust.
Studying Jedi Archive records, Dooku based his new weapon design after the curved hilts that were standard during the heyday of Form II lightsaber combat. The curve allowed the hilt to fit better into his hand, allowing for superior finesse and precise blade control.
