8. Han Solo - Star Wars: A New Hope
Han Solo's (Harrison Ford) disappearing act in Star Wars: A New Hope might well be the all-time most famous example of a character knowing it was time to hang things up, but ultimately deciding not to.
After he delivers Luke (Mark Hamill) and a rescued Leia (Carrie Fisher) to the Rebel base and collects his reward, Han along with Chewbacca (Peter Mayhew) decides to leave the Rebels to it as they prep their final assault on the Death Star, much to Luke's disappointment.
But of course, Han and Chewie eventually return in the Millennium Falcon and help change the tide of the final battle, and that basically alters the entire future course of Han's life.
If Han kept his conscience at bay and stayed out of the Battle of Yavin, he'd never have married Leia, fathered Kylo Ren (Adam Driver), or been killed by his own son decades later.
Granted, the alternative is probably Solo hanging out in some dirty corner of the Galaxy and getting killed in a cantina by somebody he double-crossed, but Han's decision to join the fight set him on a path that would end with his own death-by-patricide.