When it comes to Jedi deaths in Star Wars, Order 66 from Revenge of the Sith with never be beaten. Out of the 10,000 Jedi in the Republic, less than one percent survived the very first day of the purge, and the Order never recovered. However, because of this disastrous event, it's easy to forget just how devastating the events of Star Wars: Attack of the Clones were, as the Jedi faced their biggest loss in centuries.
With Anakin, Obi-Wan and Padmé forced into an arena for the Geonosians' entertainment, precisely 212 Jedi arrived to their rescue. Led by Mace Windu, these Jedi ranged from young Padawans to Jedi Masters (although few had ever used their skills in actual battle). And with hundreds of battle droids deployed to attack, the Jedi had no choice but to fight in an open area while surrounded, resulting in a huge loss for the Order.
How Many Jedi Survived the Attack
As the battle droids closed in and destroyed the Jedi, the remaining few were left surrounded and asked to surrender. Out of the 212 Jedi rescuers, only 12 of them were left standing in the arena, and a few more captured Jedi were pushed into the circle, including Jedi Master Plo Koon and Ki-Adi-Mundi. On top of this, some Star Wars comics have named other Jedi who aren't seen in the circle, so they either survived their wounds or successfully hid until the Clones arrived.
Overall, it is assumed that around 30 Jedi survived the attack, including some who never died on screen and are left missing. This brings the grand total of deaths to around 182, which was a staggering defeat for the Jedi and their largest loss before Order 66. And this number doesn't even include the massive Battle of Geonosis that took place right after, as even more Jedi ran into the fray with their new Clone army. Although, it's currently unknown if any died during that time.
How Many People Died on Geonosis
The vast majority of Jedi are introduced during Star Wars: The Clone Wars, so most of those who perished on Geonosis were left unnamed. But there still were some notable figures, such as Coleman Trebor, who was the only Jedi Council member to die during the battle. And those like Jedi Tan Yuster were the most tragic of all, as they were only Padawans in their young teens, and some were shot down in front of their Masters.
After the Clones arrived, it's possible some Jedi received medical attention and survived. Although the death didn't stop there, as the following battle was just as deadly for both sides. A total of 51 Clone troopers soon died on-screen, and over 200,000 droids and Geonosians are assumed to be destroyed in the carnage, especially since an entire droid transport was shot down before it left the planet.
So while the Battle of Geonosis ended in victory, the number of deaths was disastrous and a taste of what was to come. It also puts into perspective how brutal the Clone Wars really were for the Jedi, and helps explain why they so willingly accepted the mysterious Clone army that seemingly appeared out of nowhere.