Axl (アクセル Akuseru) is a playable character and the tritagonist from the Mega Man X series. He is a prototype of the new generation Reploids with the unique ability to mimic the external and internal characteristics of anyone he encounters. Axl has held important roles in two of the games he has appeared in so far, effectively making him the third playable protagonist of the Mega Man X series alongside X and Zero, as well as the tritagonist.
Axl appears as a teenager with green eyes, an X-shaped scar on his face and spiky auburn hair that sprouts outward rather than flow down. His basic armor design is somewhat similar to X with a black sheen (or indigo sheen in X7) featuring red accents. His shoulder guards are pointed and his legs feature small booster-like compartments. Jutting from his upper back are two long, white retractable "wings." His helmet design, when viewed from topside, resembles an upside down 'A' with a circular camera-like lens in the center.
Axl is cocky and has a sense of humor. Although he can be very whiny when there is nothing to do, which can get on X and Zero's nerves, Axl is kind-hearted and always cares about others. He often brags about how he is one of the best and this can get him into trouble. He is immature and naive, but he has his heart in the right place and still tries his best to fight for justice.
Axl can also be noted to have a sort of fondness for battle, which puts him in contrast with X. However, this may turn out to be a good thing, as seen in Mega Man X8 when twice he convinces X to continue fighting against their enemies, at least until the war is over.
Mega Man X7
In Axl's debut, he was a member of the bounty hunter/vigilante syndicate, Red Alert. One of his missions under Red Alert had him attacking the base of a suspected Maverick and then kill them. He managed to accomplish this by killing the suspect's second-in-command, and then masqueraded as him to let down the Maverick's defenses before shooting him in the back and stealing a briefcase that he was protecting. However, after questioning their methods, he escapes their base, and was "captured" by Zero. When the conflict between his old group and the Maverick Hunters began, Axl felt himself responsible, since Red Alert was challenging the Hunters for his custody. In order to make up for his mistakes, he joins forces with Zero and the Hunters to stop Red Alert, although they were initially reluctant to let him join. It was through Axl and Zero's combined efforts during the conflict that X came out of retirement to fight again. While working with Zero in regards to fighting Red Alert, he also explained his history with Red Alert to Zero, along with the circumstances that eventually caused him to defect to the Maverick Hunters.
Together, the three infiltrate Red Alert's base of operations, the Crimson Palace, and confronted the leader, Red, himself. After defeating Red, the Hunters learn that Sigma is at it again, manipulating Red Alert from the shadows. Even after defeating Sigma, twice, he manages to rise again and punches Axl through a wall. Sigma then swore to have a new form when he does return. Surprisingly, Red reappears, and just when Sigma is presumably attempting to possess him, Red uses Axl's pistol to blast Sigma out of the palace through a window. It turns out that "Red" was actually Axl copying his DNA to trick Sigma. X, Zero, and Axl then escape the crumbling palace.
Mega Man X8
Axl joins X and Zero in the forest outskirts of the Jakob Orbital Elevator, investigating an out of control crab-like Mechaniloid. This time around, Axl is now a full-time member of the Maverick Hunters and was trusted by both X and Zero.
After subduing the Mechaniloid, the three encounter (Axl for the first time) Vile, who kidnaps the director of the Jakob project, Lumine. After this incident, a series of Maverick attacks begin, all revolving around the involvement of New Generation Reploids. It is revealed that Axl is a prototype of these Reploids, since they all possess the same copy chip as him. Some of the Reploid Mavericks consider Axl a traitor for siding with the Hunters, as they refer to X and Zero, as the "old" Reploids.
The "mastermind" of the incident is revealed to be Sigma once again, and the three Hunters chase him to his palace on the Moon (and Sigma reveals that, even if Axl didn't side with the "old" Reploids, he still wouldn't have allowed Axl to join anyways, as Axl was nothing more than a "flimsy prototype"). After Sigma is defeated (presumably for the last time), Lumine enters the scene, much to the delight of Axl and his friends; however, this delight is quickly dispelled by Lumine's revelation that he, not Sigma, was the true mastermind: Sigma had merely helped his plan along. He reveals that the copy chips of all New Generation Reploids, including himself, contain the data of dozens of Reploids, including Sigma. Lumine then explains that Sigma rebelled against the world, but had his own reasons for doing so. So what about himself? Lumine states that Sigma's data allows for him and all the New Generation Reploids to go Maverick at will.
Axl and his friends defeat Lumine, but the latter has one last trick up his sleeve: something lashes out of Lumine's lifeless shell as Axl approaches, striking and breaking the lens on his forehead, knocking him unconscious before Lumine's shell is destroyed by X and Zero.
When the group begins their descent back to Earth, a comatose Axl is carried in X's arms. In his broken forehead lens shines a fragment of what Lumine hit him with.
Mega Man X: Command Mission
Axl is now promoted to class S Hunter status. He heads to Giga City a short time after X and Zero did, believing that his copy abilities may have originated there. He joins X's party midway through a mission to infiltrate Mach Jentra's Ulfat Factory. Also, he tells X that someone was using his copy ability to mimic Wild Jango to infiltrate Giga City shortly after they defeated Jango a second time (the culprit later revealed to be Colonel Redips himself). Presumably, his copying abilities grew stronger, as he is now able to copy many of the bosses DNA and transform into them, whereas it was mentioned in X7 that he can't copy bosses, just their abilities.