The last ten minutes of that movie were the sappiest scenes, making everyone feel a bit awkward.

sappiest 是形容词 sappy 的最高级形式。sappy 由名词 sap（树液）加形容词后缀 -y 构成，原指"像树液一样黏稠的"，引申为"过分感伤的、煽情的"。sappiest 表示"最煽情的"。