Mighty the Armadillo


Canon

Mighty the Armadillo is an anthropomorphic armadillo, first appearing in an obscure track-ball controlled arcade machine, SegaSonic the Hedgehog, and subsequently Knuckles' Chaotix for the Sega 32X, followed by a long absence until Sonic Mania revived him as a DLC character.

My Read

Mighty's characterization is basically absent within the games, if you don't bother to read the manual or what ever other supplementary documentation exists to describe him. As you can tell, I don't care to; I value Mighty as a blank slate for which little is set in stone. This makes my headcanons for characterizing him about as valid as heacanon can be.

My main informer for his characterization is, ironically, this very lack of appearances. Without going full fan theory, maybe Mighty does not draw the limelight to himself much in-universe? Heroic like much of Sonic's supporting cast, yet he does not find himself in the role of vigilanteism. He is often occupied looking after those closest to him, but this does not have to mean that he only looks out for him and his own. Mighty's heroism could show behind the frontlines, providing humanitarian relief, or more friendly-neighbourhood heroics for those who lack the voice to publicly praise him (similar to the heroics Amy tends towards, only less often drawing him into whatever Sonic is doing).
So yes, some of Archie's pacifist interpretation informs this too.

This is getting out of the territory of characterization, but I want to touch on Mighty's abilities - notably his assumed arm strength. This has no basis in any of his gameplay to date, and seems entirely based on his name. I prefer to interpret his 'mightiness' as defensive strength, since it's in theme for his species, reflects at least in his Mania gameplay, and because it's a skillset that actually sets him apart from every other srength feat machine.

TL;DR Mighty is a quiet paladin. Stoic and nurturing, he's more Piccolo than Knuckles ever was.

Fanon

Mighty is quiet but highly perceptive, as shown by events following the disbanding of the Original Chaotix. Though Heavy and Bomb were blamed by the group as plants by Robotnik to slow the team down, Mighty discerned the two robots were sincere in their rebellion from Robotnik (even if this was the result of a stress test on the robots' artificial loyalty by the doctor, purposely choosing badniks that were incompetent), he and Ray teaming up with the two later. There was actual evidence of a mole within the Original Chaotix which hastened the group's breakup, and Mighty suspected the leaker was Charmy the Bee instead; he was right in his suspicion, albeit that Charmy was unknowing of his role.
Charmy is an advanced android in the BN Series of badniks, a mass produced model of which could be encountered during Robotnik's occupation of Flickies Island.a

Mighty has at times worked within the humanitarian division of G.U.N, but his knack for sniffing out secrets made him a poor fit for the organization. G.U.N are currently seeking 'information' from him and Ray, leading to the two going into hiding, formally declared missing from their home in the United Federation.1

During the events of Sonic Heroes, Mighty and Ray were aproached by a disguised Metal Sonic (a time-clone of the original fought on Little Planet, not the repaired Metal Sonic Kai) to form "Team Sonic", (Mighty not yet having met Tails, nor knowing that Sonic had met Knuckles) in order to foil Metal Overlord's plans, but were unsuccessful.b If Mighty figured out Metal's ruse (which is likely), he has not yet revealed Metal's identity or existence to anybody.

Mighty has few ties to Sonic's allies, only knowing Sonic and Knuckles (and, briefly, Team Sonic and the Chaotix through the two), but his links with these two go back a long time. Sonic helped Mighty and Ray escape from Dr Robotnik before he met Tails, and Mighty was the one to give Knuckle's his shoes and gloves before anyone else from outside Angel Island made contact. Mighty's reticence and rare contact with either Sonic or Knuckles leaves many surprised when the two express their respect for him.