Toko New Years Challange One
It's all because of his messed up family. Toph had long decided that had Zuko been born to a normal family, he would have been a lot less driven. He would have been content to be who he was and not try to be anyone else. He wouldn't have pushed himself to run around after a lost cause, drilling himself endlessly to try and win the favor of a father who never cared about him. He wouldn't have known the pain of losing a parent and knowing that it might have been his fault that she left. He would have never known that siblings lied and cheated and schemed to kill you, and would hide it behind a smile.
Even his uncle was pretty messed up. Toph knew Zuko just considered him a sweet, lovable, lazy man who represented good. If he only knew what the Earth Kingdom knew, that thousands had died under the man's hand, before he turned back at Ba Sing Se. That was the man that had taught Zuko good.
Had Zuko been born to a normal family, he would have been boring and weak and complacent. Zuko's messed up family made him strong, made someone Toph could actually respect.