His submissiveness makes him always accept others' opinions without question.

submissiveness 是由动词 submit（顺从、屈服）加上后缀 -ive（表示"具有...性质的"）构成形容词 submissive（顺从的），再加上名词后缀 -ness 构成的名词形式，表示"顺从的性格或状态"。