What kingdoms contains heterotrophic organisms?

Animals (the animal kingdom), by definition, are multicellular and heterotrophic. Animals cannot produce their own food. They feed on other organismal sources for their energy. They feed on plants or other animals. Thus be their definition of heterotrophic. All animals (whether Chordata, Echinodermata, Porifera, Placozoa, Annelida or Arthropoda) are all heterotrophic and all multicellular. Even tiny things like placozoans and rotifers are multicelled.

Fungi cannot produce their own food either. Thus they may be called heterotrophic. They acquire their food by growing in it. Thus they acquire the label saprophytic as well. The fungal kingdom features both unicellular and multicellular organisms. Toadstools, mushrooms, bread mould, fruit mould and such are those that are multicellular.