Mmm, I like avatar, but zuko would actually be an example of it done poorly. He was a great starting villain, and him freeing aang was a great reveal that the show had depth, but everything with his 'backstory' was exactly the sort of cheesy that ruins immersion. It lost that feeling of depth when you started getting 'good character / bad character' contrasts. It relied on the firelord (bad character) being one dimensional evil, while zuko had a good (character) mother so he could be good, too. Until he and Iroh were alone together, and then the whole 'humanized villain' idea became quite good. You were able to see zuko experience things and adapt, as a character/person should, not just some post-hoc explanation for the present. I'm not going to rag on avatar for the cheesy bits; it was a kid's show, and even adults sometimes need to be hit over the head to grasp things. It still wasn't an excellent example of villain writing.