'Pathetic' means weak, poor or inadequate when referring to a person or their performance. It can also apply more generally to a group performance or situation. 'Apathetic' means unresponsive, disinterested, or lacking in energy or enthusiasm, and usually refers to the mental or psychological state of an individual or a category of people. A doctor, psychiatrist or psychologist might describe the condition of a patient as 'apathetic', due to illness, sedative drugs, or depression.

pathetic describes one that's wretched apathetic describes one that compationate to something

"Pathetic" is normally an adjective. "A" is normally used before a (substantive) noun. If you could provide a little context, someone might be able to help you.