Walter White is a metaphor for cancer
In Breaking Bad, Walter is diagnosed with cancer and he progressively becomes a bigger and more powerful drug lord, this is why I think Walter is an actual metaphor for cancer.
His growth: Walter begins as a very small and inexperienced meth cook, similar to how cancer starts off as a small and unnoticeable cell in the body, and his growth affects the people around him even causing deaths which is similar to how cancer affects/kills the patient, it’s also believed that Walter was always secretly a bad person but never showed it until he got cancer, this is similar to how cancer can go unnoticed for several years
Metastasis: Walter’s actions affect the people around him as said in the last part, the most notable affect happens when he lets Jane die, when her father finds out, he becomes depressed and causes the two planes to crash into each other, killing a bunch of people, this is the ripple effect Walter causes, which is similar to metastasis where the cancer spreads across the body, he technically also causes the death of Combo unintentionally due to Walter wanting them to sell the meth on the streets
Erosion/Acceptance: Walter progressively becomes a bigger and bigger jerk to the people around him and eventually fully becomes Heisenburg, this is similar to how cancer deteriorates the patient’s body to the point of no return and how the patient comes to terms that they can’t be cured
So in the end, Walter wasn’t just diagnosed with cancer, he is the cancer