Burgermon isnt the only good and kind monster in Kamen Rider series. There are others just like him.

Roidmude 072, a bat-type Roimude who took the form of Kyu Saijo, an SIU Researcher in Drive Series.

Second is Gazai Gamma, nicknamed by Akari as Cubi-Chan in Ghost Series.

Lets not forget the Mole Beastman. A kaijin who became ally in Kamen Rider Amazon (Showa) series.

And Mamoru, a Mole Amazon who is an ally in "Kamen Rider Amazons" series, later he became villain in "Kamen Rider Amazons Season 2" series.