What makes characters memorable?
1. You character MUST be driven by a yearning for something specific.
Inigo Montoya wants the six-fingered man. The Prisoner wants to escape. The Fugitive wants to prove his innocence.
This must be specific, not abstract. A "peaceful life" just won't cut it, but a "peaceful retirement from a life of killing to enjoy with his new wife" is more to the point and worth fighting for.
2. You character needs to have incidental traits.
Kojak sucked a lollipop. Sheldon cries out "Bazingo." Indiana Jones hates snakes.
You get the point.
These incidentals can become plot points, but they don't have to. They primarily make your characters more real. I store these kind of details in my head when I notice them in real people I encounter, but I know other writers who actually keep a journal of these observations.