The Question and Answer section for Paper Towns is a great resource to ask questions, find answers, and discuss the novel.
This is the only quote I can find that seems to "describe" Quentin the way Margo sees him.
God I can’t believe I used to think Quentin Jacobsen was like a superhot, superloyal defender of justice.’ But then —you know—you kind of were.”
1) Q and Margo’s discover the body of Robert Joyner in the park.
2) Margo goes to Q’s window and wants him to go with her to get revenge on her former boyfriend (he dumped her).
3) Margo disappears.
4) Q looks for clues as to where Margo has...
What chapter are you referring to?