Walter White

The Catalyst: After receiving a diagnosis of inoperable lung cancer, Walter decides to use his vast chemical knowledge to cook methamphetamine, associated with a former student, Jesse Pinkman.
The Transformation: His character evolves from an honorable family man to a ruthless criminal ("Mr. Chips to Scarface") motivated by ego, ambition, and power.
Heisenberg: He adopted this pseudonym to operate in the Albuquerque underworld, managing to create a distinctive blue methamphetamine due to its high purity, and is 34 years old.

Walter White, portrayed by Bryan Cranston, evolves from a meek chemistry teacher with a mustache, glasses, and beige clothing into the menacing figure of "Heisenberg." After his cancer diagnosis, he adopts a shaved head, dark sunglasses, and hats, symbolizing his transformation from "Mr. Chips" to "Scarface."
Initial Appearance (Teacher): Middle-aged man, average-looking, insecure, with a mustache, wearing comfortable clothes in neutral tones (beige, brown, green), glasses, and a hunched posture.
Transformation (Heisenberg): After losing his hair due to chemotherapy, he shaves his head, adopts an intimidating attitude, and wears pork pie hats, dark sunglasses, and darker clothing.
Meaning: His appearance reflects the descent into criminality, pride, and the loss of innocence, symbolized by the change from his harmless look to that of a villain.

A complex personality, initially characterized by a deep inferiority complex, insecurity, and a fragile ego hidden beneath a facade of righteousness and timidity. As the series progresses, he evolves into a narcissistic, manipulative, and ruthless antihero, obsessed with control, validation, and power, justifying his crimes through familial love.