There are many fictional characters across various forms of media who undergo major personality changes after facing hardships. One prominent example is Ebenezer Scrooge from Charles Dickens' novella "A Christmas Carol." Scrooge, initially portrayed as a cold-hearted and miserly old man, undergoes a transformative experience on Christmas Eve when he is visited by three ghosts who show him his past, present, and future. These visions of his own life and the potential consequences of his actions lead him to realize the error of his ways and to change his selfish and greedy behavior. He becomes kinder, more compassionate, and generous, embodying the true spirit of Christmas.
Another example is Walter White from the TV series "Breaking Bad." Walter White starts as a mild-mannered high school chemistry teacher who turns to manufacturing and selling methamphetamine to secure his family's financial future after being diagnosed with terminal cancer. As he gets deeper into the world of drug dealing and faces numerous challenges and dangers, he gradually transforms into a ruthless and manipulative drug lord known as "Heisenberg."
Keep in mind that personality changes after hardships are common storytelling elements in literature, movies, and TV shows. These examples are just a few among many characters who undergo significant transformations due to the challenges they face.