This is not a grammatical Italian phrase: “promise” is English. The likely intended Italian phrase is “promesso che lo avrebbe fatto, ” meaning “promised that he or she would do it.”
Mi promise che lo avrebbe fatto per me.
He promised me he would do it for me.
Mary promise che lo avrebbe fatto per Tom.
Mary promised that she would do it for Tom.
Mary promise che lo avrebbe fatto per noi.
Mary promised that she would do it for us.
He promised he would.
Mary promise che lo avrebbe fatto per me.
Mary promised she would do it for me.