He always talked big, but never amounted to anything.
他总是夸口,但毫无成就。
talk big: speak boastingly; make exaggerated statements or excessive claims in order to impress people 说大话;吹大牛;言过其实;以期引人注目。
再如:
We dislike those who talk big and do nothing.
我们不喜欢那些专讲大话而不做事的人。