Chojin Sentai Jetman (1991)

Both feature villainous organizations where the higher ups constantly argue and one up eachother. In RX they do sever a leader while in jetman they are all trying to become the top dog

Both feature a team color (red, blue, yellow, black, white)
Both have dimensional villains with monsters mixed with items and animals
Both have ranger girlfriends that turned evil

Both have the same color pallet teams
Both have rangers die in the season
Both feature monsters made from objects
Came out 10 years apart

It's the very first Super Sentai series what made many of it's successors possible. If you want to watch the original first season of the Super Sentai series.

It's the 14th sequel of the series from Super Sentai right after Chikyu Sentai Fiveman which is the 13th sequel. If you would like to watch the super sentai series chronologically.

It's the 15th sequel of the series from Super Sentai right after Chojin Sentai Jetman which is the 14th sequel. If you would like to watch the super sentai series chronologically.