There are many synonyms for the phrase "weakness flesh" that can convey similar meanings with slight variations. Some popular synonyms for this phrase are frailty, feebleness, vulnerability, infirmity, fragility, delicacy, susceptibility, and debility. These synonyms highlight the physical limitations and shortcomings of the human body which can often lead to vulnerability and weakness. While they may differ in their connotations, all these words refer to the inherent weakness of the flesh and the susceptibility to illness, injury, and aging. Using synonyms can bring variety in the text and make the message conveyed more profound.