Psychic also had an immunity to Ghost in Gen 1, but Ghost became super-effective to Psychic in Gen 2. --- Why do people... betray one another? They might as well... all just die instead. Welcome to my kingdom!
Strictly speaking, there is a Pokémon immune to Ice, Bug, and Steel. (Shedinja.) So the answer: Dark, Rock, and Flying. --- Creator of Jay's Journey (see quote!) "It's not ten years old! Therefore, it sucks!" - Nostalgia whores everywhere