I think you have to find the humanity in the character and then the deterioration is a part of the process - the journey of the character. It's like playing King Lear. You can start off as a nice old man who finishes up crazy.
I'm always watching people over a short time frame, putting them in an extreme position. Sometimes you don't see the humanity in a person because the time frame is so short and the circumstance so extreme.
It would be nice to feel that we are a better world, a world of more compassion and a world of more humanity, and to believe in the basic goodness of man.
What is tolerance? It is the consequence of humanity. We are all formed of frailty and error; let us pardon reciprocally each other's folly - that is the first law of nature.
France, for example, loves at the same time history and the drama, because the one explores the vast destinies of humanity, and the other the individual lot of man.