Welcome to Smogon! Take a moment to read the Introduction to Smogon for a run-down on everything Smogon, and make sure you take some time to read the global rules.
I think it's safe to say Psychic was the best type in RBY. Due to its one weakness, it was practically unopposed and the very limited amount of bug-type moves only aided its ascension. There were only a few move that were super effective on it, Leech Life, Pin Missile, and Twineedle. Of the...