21. Severus Snape (Harry Potter series)
The first of two book characters to appear on this list (unless you count Iago), Snape is by far the most complex character in the Harry Potter series, with a timeline of events in his life spanning from when HE was a child, up until the modern day of the final book in the series, in which he dies. Going historically through his past, he really does have a sad tale to tell. He was in love with Harry's mother from childhood when he was a weird outsider and she was unaware of the wizarding world, but she fell in love with a man that Snape hated for making his life hell. So Snape fell in with a bad crowd and wanted Lily for himself, allowing for the death of James under the condition that Lily would be protected...and Voldemort didn't make that happen. So Snape, admittedly a vile person, started on the road to redemption by begging Dumbledore for help, and in the end, this led to Snape being despised by the son of the woman he loved for years, simply because he could never tell him the truth about what laid in the past. He kills Dumbledore and is made a pariah, but in the end it turns out every foul mood or negative action he caused was done for a purpose, and he was trying to atone for his sins. It really makes it a noble gesture that Harry names one of his sons for Severus in the epilogue, as much as people hate said epilogue's existance.