Ben manipulates Locke from their first meeting, because Locke represents what Ben can never be -- someone the Island genuinely chose. Ben was never special; he seized power through cunning. Locke was special and didn't know what to do with it. Ben murders Locke off-Island in one of the series' most shocking scenes, then watches the Man in Black wear Locke's face as a cosmic punishment. Ben's arc ends with genuine remorse -- he stays outside the church in the finale, not yet ready to forgive himself.