Aaron Eckhart stayed in a place of "rage" for years after playing villains in movies.
The 45-year-old actor took on the role of baddies in 'The Dark Knight' and 'The Black Dahlia' and decided not to play anymore evil characters until being offered the lead in 'I, Frankenstein' as the monster, who he says is actually more of a good guy.
He told the New York Post newspaper: "Acting those rough roles means research. I stayed in that place of animalistic rage for years.
"Life is not all black and white. It's complicated. We're complicated human beings. Even if Aaron's a good person, all that other stuff is part of being alive."
The 45-year-old star is happy to be playing a complex character in the upcoming Stuart Beattie movie which he says he can relate to.
He explained: "We're damaged, flawed and trying to learn from it. No rhyme or reason to many things we do.
"It's part of what happens after you're born. Sometimes one part comes out, sometimes another and you put that other part back in.
"On Earth, everyone needs someone. We all want to be included. And so does this particular character I play."
The actor admits although he's found it fairly easy to get into character as the monster, putting on the costume has been more of an effort.
He added: "Every day it took three hours in the makeup room putting the stuff on. Making scars and stitches. Sticking wigs on. Looking in the mirror, you'd think, 'Oh, God' then you'd rip it all off in 10 seconds because you wanted to get home."
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