I was thinking about Poison-types, and the type in general seems worse-off over every other type. It has only one type (Grass) weak against it, a plethora of things resistant to it, and two types (including itself) that are immune to it. It has the Poison status effect going for, but almost every type has a member who can inflict that, and two types again can't be poisoned. The only other things it has going for it are only two weaknesses and immunity to other Poison-types and Poisoning.
On the other hand, Steel boasts only three weaknesses, a resistance to almost everything else (including the only resistance in the game to Dragon-type), and an immunity to Poison-types.
Grass-types have five weaknesses (including the only one to Poison-types), and even more things resist it, whereas Electric-types have only one weakness.
So, do you think that the typing system in general can be unbalanced and unfair on occasion?