Imagine you're doing a survey. You show someone a picture of a stranger--something with a little bit of personality--and you ask them to describe the person they see. They won't tell you much at first, but with urging, they'll begin to fill in the gaps, and eventually, they'll become so sure of their assumptions that it will be hard to convince them they're not true--even if they are introduced to that person in real life. That is what has been happening with Nick Blaine for the past five years. We know nothing about him, save for one short flashback, but if you were to survey a group of fans, they'd tell you all sorts of wild tales. Some think he's the perfect knight in shining armor, far superior to Luke; others will shrug and say they don't know; the rest will swear up and down that they physically saw him devouring an infant under the full moon.
Nick is like any other character in the franchise. He's complicated, and he's modeled after a real person, not a fictional love interest. That means he's contradictory. Sometimes his actions and beliefs don't follow a logical pattern. You'll never be able to fill in the gaps. No stereotype will fit. He's not 'one of those' no matter what definition you'd apply to that phrase. The franchise never does bad or good, either. They're never going to write in a person that you absolutely love. They're always going to have some flaw, some demon, some shady past--and it will probably be enough to sour them in our eyes. Not everyone can be comfortable with that. They want black and white, square pegs for square holes, and if that's not what they're given, they'll grab a chisel and start whittling away at that peg until it fits.
We do have clues about what's going on inside his head and who he is. But they pose more questions than answers, and it's never enough to give us the full picture. There's always something missing--some integral piece that could finally define the man behind the eyebrows. Perhaps we'll learn more. For now, we'll just have to go with what we've been given.