Complacence, Complacency, n.
Etymology: [LL. complacentia: cf. F. complaisance. See Complacent, and cf. Complaisance.]
1. Calm contentment; satisfaction; gratification. The inward complacence we find in acting reasonably and virtuously. Atterbury. Others proclaim the infirmities of a great man with satisfaction and complacency, if they discover none of the like in themselves. Addison.
2. The cause of pleasure or joy. "O thou, my sole complacence." Milton.
3. The manifestation of contentment or satisfaction; good nature; kindness; civility; affability. Complacency, and truth, and manly sweetness, Dwell ever on his tongue, and smooth his thoughts. Addison. With mean complacence ne'er betray your trust. Pope.
Shades of meaning
Fernald lists complacency only as an antonym, under pique, repentance.
He lists it without comment; the entries above explain its neighbors.