Quint dies in the novel (he gets pulled out to sea by the shark a la Ahab). And in my personal opinion Jaws is one of the few times the film is vastly superior to the book. The book was a mess with the mafia, impotent Brody, the arbitrary and pointless affair between Mrs. Brody and Hooper that was only there to make Hooper unlikable (and thus justly shark chow).
The film streamlines it to an amazingly taught story and above all it gives a reason for Quint's strong vengeance on sharks--the Indianapolis. Not in the book. I wouldn't say Quint has an arc really. His arc happened in 1945 when he went int the water with a life jacket. With that said he is an amazing character and, along with the score, steals that amazing movie.
***
As for Scarlett O'Hara. Yes, she is a manipulative, conniving, cunning *****. And that's why we (the audience) has to love her. She is one of the all-time great female roles and Vivian Leigh runs away with film history in her hands in it.
She goes from being a spoiled, bratty, flighty airhead to growing into a strong, intelligent, and masterful survivor. Her trip from Southern Belle to "As God as my witness..." is breathtaking. Her ability to kill, hide murder, and maintain her wealth by playing everyone (including Rhett) is a sight to behold. Sure, her one weakness is her pathetic obsession with Ashley Wilkes that ultimately undoes her only after she realizes the error of her ways, but that only completes the arc where she can finally let go of her Southern belle fantasies of a South that's gone (not that it ever historically really existed

) only to still lose everything in the end.
A tour de force. Michael Corleone is also absolutely despicable by the end of the second film, but what an amazing journey from clean war hero to empty monster. A journey that cinema made unforgettable and truly remarkable to watch.
Alec Guiness in Bridge on the River Kwai, Tim Robbins in the Shawshank Redemption, and Jimmy Stewart in It's a Wonderful Life are also worth mentioning.