Perhaps the single strangest thing about comics is having to come to terms with the fact that some of the most interesting and loveable characters lacked their most compelling features when they were first introduced.
With Daredevil, Deadpool, and even the iconic Punisher having some less than stellar beginnings, it's honestly shocking that so many popular superheroes only developed their most iconic incarnations midway through their history on the page.
It's one thing to write a likeable character, but it's entirely another thing to write a previously hated character and change fans' minds on them. That said, often this is less a task of monumental proportions, and more one of introducing unexplored aspects of the character - such as the Iceman's life outside of him being in the X-Men, or The Question outside of him being used as a way to espouse his creator's political musings.
There are dozens of writers and artists who could stake a claim to have changed their characters for the better, and yet most tend to get overlooked.
While there is no one consistent way to judge a character's 'redemption' in the comic world, it's always worth appreciating the decisions that improved and fixed characters who were once found wanting.