As the deuteragonist of Hajime Isayama's Attack on Titan manga and its soon-to-conclude anime adaptation, there are few characters as pivotal to the story's course as Armin Arlert. From his humble beginnings as a Shiganshina resident who joined the Survey Corps after the destruction of his hometown, to his struggles with his stature and physique during training, Armin has forged a place for himself among Eldia's protectors with his keen intellect and perseverance. Now, as the holder of the Colossal Titan, he is arguably also one of the most powerful characters in the series, and perhaps the second most important weapon in Eldia's arsenal.
Having been saved by the Titan serum in place of former Commander Erwin Smith, there is now a heavy burden resting on his shoulders. The sequence of events following the operation to retake Wall Maria firmly positioned him as a key player in Paradis' resistance against the threat posed to their existence by Marley and the rest of the world. After Eren's triggering of the Rumbling at the end of Season 4 Part 2 of the anime, Armin has a difficult road ahead to stop his best friend from committing genocide while also saving his homeland from destruction by enemy forces. With the Attack on Titan finale about to air this year, it is worth delving into the role Armin will play in concluding the story, and how this will affect the fate of the islanders and the rest of the world.
The Scouts' Main Strategist
Even in spite of his limited physical prowess, Armin has proved on multiple occasions that he is as essential to the Scouts as any of their strongest fighters. What he lacks in athleticism and killer instinct, he more than makes up for with his innate eye for detail and ability to pick apart extremely adverse situations in order to choose the best path towards victory. This can be observed as far back as the Battle of Trost, and it will come as no surprise if the remaining members of the Scouts and the Marleyan Warrior unit rely on his tactical insight to take the fight to Eren and his army of Wall Titans. Moreover, Armin is also a commanding orator when required, and his ability to rally both hostile camps and resolve conflicts between them, might also play a role in the course of the battle.
Hence, it is quite likely that the final confrontation to decide the fate of the world will hinge on Armin's ability to come up with a plan to counterattack the immense power of Eren's Founding Titan. Since a frontal assault would amount to nigh on suicide, the Scouts and Warriors will need a detailed plan of attack to turn the tide of the battle in the face of the massive disadvantages they face in terms of numbers and sheer destructive power. This is not a new situation for Armin, who has always managed to find a way out of scenarios where survival seemed virtually impossible. Not one to shy away from danger in any form, Armin's strategies often gamble lives for huge payoffs, much like Erwin Smith, as seen in his ploys against Bertholdt's Colossal Titan during both the Clash of the Titans arc and the Return to Shiganshina arc. The latter was an instance where Armin was more than willing to sacrifice his own life for Paradis' cause, and there is chance that he might face this grave choice once again when contending against the might of the Rumbling.
A God Of Destruction
In addition to his prowess at outmaneuvering his adversaries, Armin is also the holder of the Colossal Titan, described as a "God of Destruction" by many who have faced him and lived to tell the story. Boasting a transformation with explosive power that has been likened to that of a nuclear weapon on many an occasion, Armin's most devastating use of this ability came during the Raid on Liberio. Deployed without any other Scouts to support him, Armin unleashed his titan transformation at the port of Liberio, a site where a considerable portion of the Marleyan navy's fleet, alongside vessels from other nations were docked. In less than an instant, he was able to decimate all the forced assembled there, with the blast from his transformation sending shock waves that razed settlements located further inland.
There is no doubt that Armin's abilities as the Colossal Titan will play a crucial part in dealing with the advance of the Wall Titans. This may manifest either solely in his brute strength, being able to crush entire battleships, or in his ability to emit immense amounts of vaporizing steam, as the combat abilities of the Wall Titans have yet to be fully ascertained. However, it is also worth speculating on what role he will play in the final confrontation with Eren. The Colossal Titan "nuke" as it has often been referred to, will probably come into play when the Scouts confront Eren's gargantuan Founding Titan, with is massive skeletal form. As its sheer size dwarfs even that of the Wall Titans — whose stature is on par with Armin's titan — Eren's final titan form will not be easy to take down, and the immense strength of the Colossal Titan will definitely have a part to play in this confrontation.
Saving His Best Friend
Apart from these aspects of his character development, the most pressing conundrum that Armin must now deal with is the prospect of killing his best friend, Eren. This dilemma has plagued the remaining members of the Scouts and the Warrior unit ever since they embarked on their last ditch effort to save the world, with the two factions coming to blows when tensions got heated. Although Armin is well aware that Eren will keep fighting and moving forward until his last breath, he also retains a sliver of hope about reasoning with him to bring an end to the needless bloodshed that is currently underway. In many ways, a full-on confrontation between the two is yet to actually occur, and it is quite likely that one of them will meet their end at the hands of the other if there is any hope of resolving this conflict.
Armin's sensitivity and empathetic nature have always hindered his ability to truly throw away as humanity — a quality that believes to be essential in the creation of a great leader. In fact, he is often very critical of himself even when it comes to the smallest of errors in judgement. This makes the prospect of killing his best friend all the more difficult, even his views on morality are far from black and white. Notwithstanding all this, he is more than capable of executing underhanded schemes and making tough decisions when it counts, a quality that both his closest friends Eren and Mikasa have known from the very start. Regardless of whether he does land the final blow on Eren, or instead manages to talk it out with him, Armin's role in the story now, at its very core, is to live up to the sacrifice that was made for him to go on living instead of Erwin Smith — a challenge, that he is quite likely to rise up, much like he has done at every point in the story of Attack on Titan so far.