The film succeeds in characterizing an ordinary person's struggles and growth through nuanced performances.

characterizing 是动词 characterize 的现在分词形式。characterize 由词根 character（角色、性格）和动词后缀 -ize（使...化）组成，意思是"刻画、描绘...的特征"。在句中表示"通过表演来展现人物特征"的动作。