My knowledge of Kaijus go to just the main Godzilla movies and the Gamera heisei trilogy lmao.

I would probably put every Kaiju from the Heisei Gamera trilogy, I loved Gyaos, Legion and Iris as antagonists.

Other than them? My mind went to Shin Zetton from Shin Ultraman, my only connection with Ultraman sadly lol I really wanna enter to the series.