Tā de yǔyì yuèláiyuè fēngmǎn, bùzài xūyào biérén zhīchí.
His wings grew stronger and stronger, and he no longer needed others' support.
Tips
usage
羽翼丰满 (lit. 'wings fully feathered') is a very common idiom meaning someone has grown capable and independent, or an organization has become powerful. Used both for individuals coming of age and for political or organizational power.