Cobb — the man who performed inception, the man who lived through it
On the surface Cobb is the apex of his profession: an extractor at the top of his game. But the real weight he carries is not skill, it is guilt. His wife Mal, with whom he spent fifty years in Limbo, could not shake the conviction that 'this world is fake' even after returning to reality, and killed herself in front of him on their wedding anniversary — and the film's true wound is that the person who planted that false certainty deep in her subconscious safe was Cobb himself. Late in Limbo he confesses this to Ariadne and articulates his own discovery: an idea, once inception'd, holds in reality too and cannot be undone. The trace of that regret shapes how he runs the Fischer job. Plant a single line, but make it connect naturally to Fischer's own arc of self-growth — so it doesn't gnaw at his life the way the false certainty gnawed at Mal — by placing his father's real will and his childhood pinwheel inside the layer-three safe to dress the plant as a reconciliation. The asymmetry of Limbo perception is also central to him. Mal and Saito both came to believe Limbo was reality, but Cobb knew throughout that it was a dream, so after wandering decades to find Saito his face hadn't aged. The reading that his real totem might be the wedding ring rather than the top dovetails exactly with this asymmetry: the ring he removes in reality and unconsciously wears in dreams is the proof that his conscious mind let Mal go but his unconscious never did. So in the ending, walking away from the top to run to his children isn't 'refusing to check the truth' but 'choosing the present with my family over the truth' — the resolution Nolan himself confirmed in interviews around the release of Oppenheimer.