No , most protists are unicellilar , some are colonial.
Animalia is the kingdom that consists only of complex multicellular eukaryotic organisms.
Domains Bacteria and Archaea only have single-celled organisms, such as bacteria and archaea, which lack membrane-bound organelles and nuclei. These organisms exist as individual cells and do not form multicellular structures.
Animalia contains only multicellular organisms.
The kingdom of protists has both heterotrophs, autotrophs, and uni/multicellular organisms.
Fungi And Protists
The animal kingdom consists of only multicellular heterotrophs.
The kingdom Monera consists of unicellular organisms.
plantea
The fungi kingdom contains non-photosynthetic multicellular organisms that digest their food externally. Examples of fungi are yeasts, smuts, molds and mushrooms
Multicellular and motile organisms belong to the kingdom Animalia. This kingdom includes a diverse range of organisms that are multicellular, heterotrophic, and capable of locomotion at some stage of their life cycle.
The cell kingdom that includes both multicellular and unicellular organisms is the Protista kingdom. This kingdom consists of various types of eukaryotic organisms that do not fit into the other major kingdoms (Animalia, Plantae, Fungi). Some protists are unicellular, while others are multicellular.
The kingdom that multicellular algae are categorized under is Plantae.