>>32910448There are a lot of mons capable of soloing the game all by themselves and it's not limited to Gen 1. The game becomes incredibly easy this way beause all the experience goes to one Pokemon that becomes ridiculously overleveled as a result.
Gen 1 Psychics actually had one flaw that prevented them from being overpowered: they resisted each others' Psychic while not having anything to hit each other supereffectively for obvious reasons, which made Psychic vs Psychic fights tedious, to the point Psychic was considered more of a defensive type that discouraged spamming the main attack in favor of status moves and secondary STABs. Most Gen 1 Psychics also having poor-to-okay Physical bulk also made them vulnerable to Normal types, who could tear them apart with their physical STAB. Most Gen 1 competitive people in fact consider Normal to be even more overpowered than Psychic since they had ways to consistently get past Normal resists (Rock and Ghost) unlike the latter.