A bit of a weird choice, but I'm recommending Pachirisu to move up to C-rank
Availability: 0 Badges
Movepool: Absolute garbage
Comments: Where do I begin. You can get Pachi the moment you get two pokemon, she's readily available as long as you don't get rekt by that 50% chance for Zigzagoon. Her movepool's absolute garbage, but what's important is what moves she gets. The moves of note are Nuzzle/Super Fang/Charge Beam, and Sweet Kiss to a smaller extent. Nuzzle comes incredibly early on, and is the go-to move you'll be using for Pachi. The parahax lets you draw out the battle a bit longer, and let either Pachi build Charge Beam boosts, or someone else from your team boost up. Add Sweet Kiss if you want to be mean, and you have someone who can help you sweep early gym leaders relatively consistently. Super Fang is useful for chipping damage from the bulky af Pulse-mons, so you don't have to sit down for a good half hour trying to take down Pulse Tangrowth. Later in the game, Pachi still stays relevant by virtue of its pickup ability helping you get Rare candies to sell/healing items after battles, so even when she's not in battle, she provides utility for the team. She has a niche that no other mon shares, and I feel that it's enough to place her in C-Rank
tl;dr Pachi is good. Move her up pls