Sandile
Availability: Reasonably early in the game; at Route 9
Stats: The Sandile line is prety consistant throughout their evolutionary line, in that they have high attack stats and decent speed stats. Krookodile is also acceptable when it comes to bulk, although Sandile and Krokorok are slightly fragile. It is worth mentioning that Intimidate makes Sandile effectively bulkier on the physical side than it looks.
Typing: Ground/Dark is unique to the Sandile line, and brings multiple advantages and disadvantages. Ground/Dark is pretty good coverage, and with early access to Bulldoze and Theif immediately upon capture, Sandile basically comes packages with decent [For the game's stage] duel STABs. However, while Sandile's typing is good for offense, it is rather lacklustre for defense. Sandile has 6 weaknesses, and only 4 resistances [Although he has 2 immunities].
Movepool: As mentioned in the typing section; Sandile effectively comes packaged with 2 Base 60 STABs, giving Sandile an acceptable amount of power for that phase of the game. Which is good, because Sandile's level-up movepool is awful until Lv 28; where it picks up Crunch surprisingly early. Beyond this, Sandile will mostly be reliant on TM's. However, as a physical attacker, and with good STAB coverage, Return, Dig and even Rock Tomb are decent coverage options which come at acceptable points. Earthquake comes either at Lv54, or just before the E4, and Dragon Claw and Brick Break are lategame TM options.
Major Battles:
Grant - Amaura is dangerous; as Refrigerate Take Down will likely OHKO. However, Sandile can destroy Tyrunt, due to resisting Bite and Rock Tomb, and Intimidate cutting it's attack; while making it very hard for Tyrunt to flinch it due to Bulldoze
Korrina - Being weak to fighting, Sandile's main purpose here is Intimidate. Better than nothing.
Ramos - The sad thing is Ramos is enough of a joke that Krokork might actually be able to beat Jumpluff or Weepingbel despite the type disadvantage. Also he's enough of a joke that someone else should be able to handle it
Clemont - Sweeps
Valerie - You can crush Mawile; who only had Dark-type attacks and is weak to Ground. Mr.Mime and Sylveon beat you, although a Moxie Sandile can deal heavy damage to Mr.Mime with Crunch.
Olympia - You sweep
Team Flare - Ground and Rock coverage wrecks Team Flare
Lysandre - Pyroar and Honchkrow are fodder. Gyarados and Meinshou beat you.
Wulfric - You actually can't do much here
Malva - Earthquake. Talonflame is OHKO'ed by Rock Tomb. You can Crunch Chandelure if you want.
Wikstrom - Earthquake
Dransa - Dragon Claw, although Noivern might outspeed you and hurt.
Seibold - Stay away
Diantha - You can destroy Tyrantum and Gourgeist. If you have Moxie, you can actually sweep after Tyrantum or Goltergheist from the Moxie boost, since M.Gardevoir comes out last and you should be able to OHKO Aurorus at +1 and Goodra at +2 with D-Claw.
AZ - You sweep.
Additional Comments: Intimidate is the better option for the majority of the game, due to a lack of large rosters in this game. However, Moxie can do more in those battles with multiple enemies. For example, you can get a lot of damage off on Mega Gyarados at +1 [Due to Intimidate], making it easier for you to deal with it. Diantha can actually be swept abusing the fact that M-Gardevoir comes out last, and Goodra would not be the response to Krookodile if Aurorus is still up. Both have pros and cons.
I'd actually say Sandile deserves B; not C. It wrecks quite a few fights.