Shouto’s transformation as a character reflects in his outer shell as much as the inner metamorphous.
Debuting his costume in the Villains vs Heros test, we are treated to see half a normal human body but the same cannot be said for his other half. His fire side is covered by an icy blocked exterior that if touched could burn you as much as fire. It’s not uncommon knowledge that Shouto despises Endeavour (unless your Deku and can’t put two and two together) and loves his mother, you could describe it as her ice trying to smother Endevaours quirk out of him.
Unapproachable, frightful in appearance not a costume that inspires security and a quelling of fear. When we get to see him in action for the first time, our intial scenes are of him steping out of the light and delving into darkness forcing himself away from the light. His glowing red eye staring forward piercing into the unknown of pure blackness and when he emerges to face Ojirou it is a terrifying scene. His eye leaving a red trail behind, half a body covered in ice giving him the appearance of a demented sociopath, if I saw this person approaching I would run and would not stop running for fear this person would kill me.
His entrance is in parrel with Endeavors with few dissimilarities, our first glimpse of him we are shown his face alit with fire giving a intimidating look, further illustrated with him stepping downward into a darkened stairwell illuminating his flames coming off of him, giving him a demonic appearance along with his natural in born features. Such endowment of fire sends out a distinct signal that he doesn’t want anyone to get close pushing away everyone around him retroactively, his flames are cool enough so they don’t burn people but who would dare touch an open flame. There are few who do this feat and are instantly rejected by him, wether it be admirer or a peer.
Their similarities of their costumes reflects both their personalities at the time, both are closed off, both reject their peers and both have their mind set on one goal, Shouto to not be like his father and Endavour to beat All Might.
Shouto’s inability to comprehend his own power was because he viewed it as a extension of his father not himself, so it was impossible to grasp it. To become a whole hero he needed to accept both who he is and not be closed off from the rest of the world, letting down his walls so to speak. Which just goes to show by strongly rejecting someone you may end up embodying what you hated yourself and only through acceptance of the situation or circumstances can you change whether it is who you are, your situation or even your relationships.