Assassin's Creed as a franchise is known for the depth and intrigue fostered by its numerous protagonists. Spanning across different continents and centuries, most of the main characters throughout the games are intrinsically linked by a shared ethos and outlook on the world.
That being said, there are some Assassin's Creed protagonists that are undeniably more influential to the creed that they collectively serve when compared to others. When considering the most influential assassins, none are quite as important as AC1's Altair and AC Origins' Bayek.
Assassin's Creed Origins - Bayek of Siwa
With the game in which he stars outlining the initial origins of the organization that would go on to become the Assassin Brotherhood, it is inherently clear as to why Bayek of Siwa is so important and influential to the assassin movement. Operating within Ancient Egypt, Bayek would be shaped by intense loss and suffering, from which the core tenets of the assassin movement would be born and consolidated.
Bayek was one of Egypt's last Medjay, a peacekeeping organization designed to protect the civil liberties of the people. These altruistic values were only exacerbated within Bayek's character upon the untimely death of his son at the hands of a sinister group known as the Order of the Ancients. Fueled by grief and a disdain for corruption, Bayek and his wife Aya dedicated their lives to hunting down and eliminating the Order, who would later go on to become the series' main antagonist force, the Templar Order.
Attracting more people to their cause, Bayek and Aya would establish the Hidden Ones, the organization that would eventually become the Assassin Brotherhood as it became more global and high-profile. The Hidden Ones established the values of maintaining free will and fighting corrupt injustice, which would translate over to the Brotherhood to become the organization's sole driving force. In this way, the sheer amount of influence that Bayek had over the assassins cannot be understated, creating both the organization itself and the main ethos that underpins it.
Assassin's Creed - Altair Ibn-La'Ahad
Being the original protagonist of the storied Assassin's Creed franchise, it can be said that Altair is as influential as Bayek in the overall history of the Assassin Brotherhood. Altair is widely regarded as the model assassin, being immersed within the creed from birth and attaining the rank of Master Assassin at the extremely young age of 25.
Perhaps most importantly, it was Altair who uncovered the treachery behind the Levantine Brotherhood's leader Al Mualim, who had become corrupted by a desire for power and was secretly working for the Knights Templar. Eliminating Al Mualim and obtaining the all-powerful Apple of Eden, Altair rose to the leadership rank of Mentor amongst the brotherhood, from which he was able to transform how the assassin's existed and operated, snuffing out this corruption that has risen in the Brotherhood.
As a direct result of Altair's guidance and leadership, the assassins became more grounded, opting away from a high-profile existence and returning to the shadows. It was Altair who proposed the assassins extend their reach, expanding across the globe and establishing guilds, all with the goal of operating and hiding in plain sight. While directly stopping a slew of Templar plots and nefarious schemes even after attaining the rank of Mentor, the influence that Altair holds over the Assassin Brotherhood is clear to see.
While it can be said that all the franchise's protagonists hold a certain amount of commendable influence over the organization as a whole, none hold the same watershed level of influence as both Bayek and Altair. With Bayek's establishment of the Hidden Ones and Altair's individual direction during the brotherhood's most tumultuous period, it is clear why the two are considered two of the most influential characters within the entire Assassin's Creed franchise.