>>56375293An anon in a previous thread did some data on all the types, and the worst type overall is Grass.
This chart accounts for effectiveness on both sides and accounts for how valuable each of those effectivenesses are. So Fire being super effective against Steel would be valued more than say Steel being super effective against Ice as Steel is a great defensive type compared to Ice.
Normal was the worst offensively and Ice was the worse defensively, however only 2 types were actually bad both offensively and defensively, being Bug and Grass, and Grass was was worse offensively than Bug where as its only slightly better than Bug defensively.