Shade's right. Provided the NPC doesn't heal the Psyduck, I have two level 10 Pokemon that all I would need to do is train them to level 20 and they'd have a 100% win chance.
Taking it down at this point should be a cake walk. The hard part may be deciding who does it.
Along those lines, I understand that Sunflower didn't confirm she had better chances than you two, but I thought we agreed that if Retal fights, he doesn't fight Route 34. I don't understand how this was allowed.