Dabi and Shigaraki

Emotional instability: At first, he acts like a "child-man." He gets frustrated when things don't go his way, compulsively scratches his neck due to anxiety, and sees reality through the lens of video games.
Pure, visceral hatred: His sole aim is to destroy everything he dislikes. He has no complex political plan; his driving force is deep trauma and the desire for the entire world to feel the pain he felt.
Growth as a leader: Over time, he leaves behind his tantrums to become a calmer and more confident symbol of terror, developing a genuine loyalty (in his own way) to his League mates.
Sense of emptiness: Shigaraki doesn't want to build a new world; he simply wants the current one to cease to exist. He is the personification of entropy.
Dabi (Touya Todoroki): The Calculating Pyromaniac
Dabi is much colder (ironically) and more methodical than Shigaraki. His evil stems not from chaos, but from resentment.
Stoicism and arrogance: He rarely loses his composure. He appears distant, sarcastic, and enjoys mocking both heroes and villains. He has an air of intellectual superiority.
Monomaniacal obsession: His entire personality revolves around a single person: Enji Todoroki (Endeavor). Dabi doesn't seek to change the world through twisted altruism; he seeks to destroy his father's legacy.
Lack of empathy: Unlike Shigaraki, who comes to appreciate his team, Dabi sees others as disposable tools. He is a sociopath who has burned out his own nerve endings and, with them, much of his humanity.
Theatricality: He loves drama. When he reveals his true identity, he does so with perfectly choreographed and well-planned media messaging. He is a performance villain.