Used attributively (e.g., "sweetheart deal", "sweetheart neckline"); generally not gradable.
Definitions
Arranged to be excessively advantageous or favorable, often through secret or improper negotiation. The firm secured a sweetheart contract that bypassed the usual bidding process.
Of a garment or neckline: shaped like the top half of a stylized heart. The bride chose a dress with a flattering sweetheart neckline.