My favorite type of character is the one who has gone through (or are still going through) the worst events of their life, but somehow find it in themselves to remain happy, and are usually the ones who put a smile on people's faces. They're just so sweet and you love that they're kind, but another reason why I find them interesting is because in most cases, these characters are the one who try to hide their backstory the most, giving them a feeling of mystery and attraction, as if their attitudes aren't just a product of good parenting or normal life experiences.
Characters that come to mind are 707 from Mystic Messenger, Allen Walker from D.Gray-Man, and most recently, Asra from The Arcana by Nix Hydra. 
