I'm right now doing Pokemon red, and my venusaur used razor leaf to opponent tentacool.
Obviously, it did critical hit, but something strange is, it says "it's not very effective"
I've hit few more tentacools now and it always says it! Tentacool's water/poison, and it is obvious that grass beats water since it had been always like that since the beginning. What's happening?
Tentacool is hurt neutrally by Grass Type Moves.