The phrase "not be able to do something to save your life" is an idiom that implies a person's inability to perform a certain task even if it is necessary for their survival. Some synonyms for this phrase include "couldn't do it if you tried," "completely inept," "utterly incapable," "hopelessly unable," "beyond one's grasp," "no chance whatsoever," "no way on earth," and "dreadfully unskilled." All of these synonyms convey the same inability to accomplish a task, highlighting the difficulty and impossibility of the situation. The phrase can be used in a variety of contexts, from describing struggling athletes to hopeless amateurs.