Suggestions by @axiomman

Shioli Kutsuna

as Asagi Kusanagi in Gamera: Wrath of Legion

Mana Ashida

as Yumi Miana in The Rebirth of Mothra

Mana Ashida

as Emi Miana in The Rebirth of Mothra

Dagahra

as Dagahra in The Rebirth of Mothra

Gigamoth

as Gigamoth in The Rebirth of Mothra

Viras

as Viras in Gamera: Wrath of Legion

Guiron

as Guiron in Gamera: Wrath of Legion

Barugon

as Barugon in Gamera: Wrath of Legion

Jiger

as Jiger in Gamera: Wrath of Legion

Legion

as Legion in Gamera: Wrath of Legion

Manda

as Manda in Gamera: Wrath of Legion

Gamera

as Gamera in Gamera: Wrath of Legion

Mothra (Mosura)

as Mothra in The Rebirth of Mothra

Gezora

as Gezora in Space Ameoba

Dogora

as Dogora in Space Ameoba

Kamoebas

as Kamoebas in Space Ameoba

Hedorah

as Hedorah in Space Ameoba

Ganimes

as Ganimes in Space Ameoba

Nessie (Godzilla: The Series)

as "Nessies" in Gorgo

Tiamat

as "Nessies" in Gorgo