Completing rhymes with:
depleting, deleting, depleting, fleeting, beating, cheating, competing, defeating, deleting, depleting, eating, fleeting, geeting, greeting, heating, keating, meeting, mistreating, overeating, repeating, retreating, seating, sheeting, smeeting, sweeting, treating, unseating, wieting
Completing sounds like:
compilations, completeness, completions