1) An ungrateful person 2) Bad houseguest 3) Gift-horse critic 4) One offering no thanks to you 5) Person made of granite 6) Persona non grata 7) Sore winner 8) Thankless fellow 9) Thankless one 10) Thankless sort 11) Thankless type 12) Thankless wretch 13) Unappreciative one 14) Unappreciative sort Found on https://www.crosswordclues.com/clue/ingrate