Aight, why is our boy chesnaught way down in B-? I'd say bump 'im right back up to B+
This guy checks so many dangerous things in the meta right now. He easily checks Bisharp, Mega Tyranitar, Mega Gyarados, Aegislash, Crawdaunt, Keldeo (with 40 evs in sp. def can take two specs hydro pump), Lando-T, excadrill, hippowdon, ferrothorn, scizor (can taunt SD+Roost), conkeldurr, and it can even safely come in on mega venusaur and stack spikes. He has plenty of options making him a bit versatile; he can lay down hazards and spike stack, Roar to phaze and stop about half of the things it checks from setting up, and Taunt to handle the other half even better. Leech Seed and Spiky Shield in conjunction can easily sap away a solid quarter of the opponent's health away, a third if they use a contact move on your spiky shield. He even has access to synthesis, and though synthesis is hurt by sand Chesnaught beats the two sand streamers anyway. Hammer Arm provides a reliable stab to smack Chansey and Bisharp, while even Wood Hammer can be used if you want to target Azumarill.
His great typing lets him resist the popular EdgeQuake combo, which lets you immediately check practically any lando-t. Chesnaught is also one of the few pokemon that can take on DeoSharpSlash cores with relative ease, doing whatever it wants against non Sub-Toxic aegislash and Hammer Arming Bisharp for the easy KO, while teammates can handle hazards and weaknesses for him.
Unfortunately, while he does have some great perks, he suffers from a lot of weaknesses, and needs some team support to cover them. Psychic, flying, poison (only sludge wave tho, not bomb), Ice, Fire, and Fairy is quite a set of weaknesses that needs to be covered.
However, I think that when these weaknesses are covered by teammates his performance far exceeds some other B+ pokemon.
Chesnaught for B+
Also, since we're talking about crawdaunt and azumarill:
They're both very similar and very different as well.
Azumarill can be a wallbreaker too, the CB sets safe switch-ins are basically limited to ferrothorn IF it has knock off and Aegislash IF it doesn't. Skarmory and defensive Mega Scizor can somewhat hope to take it on too, but really, that's about it. It has better bulk, better typing, and is simply a more independent pokemon that pulls more weight than crawdaunt does.
However, Crawdaunt is actually stronger than azumarill (pretty sure). IT has access to good boosting moves, the strongest knock off in the game (unless yveltal's is stronger? not sure), reliable priority, and a few options to toy around with, like superpower or even aerial ace to beat fighting type switch-ins, especially chesnaught.
Basically, Crawdaunt is strictly a wallbreaker, and needs more support coming in and getting free turns to set up if it chooses too. It performs the role of a wallbreaker a little better than azumarill does. Azumarill is still a super threatening wallbreaker with better STABs, better typing, and better bulk overall. Azumarill isn't limited to wallbreaking either, the AV set is definitely catching some popularity as a reliable switch-in to keldeo, and there's always the sap sipper sp. def set to check both zards. Crawdaunt is indeed better strictly for wallbreaking, but it's not a pokemon you can fit on practically any team, like azumarill is.
But its power is insane, its STABs are reliable, its priority is amazing, it has access to two great boosting moves (but don't use dd guys :I ), and it can even provide utility with knock off. Just in testament to his raw power, I'd say Crawdaunt is a solid B.
And while I'm here, I'll just address mega medicham again. But I actually won't I took way too long.
Basically, he can't switch into anything, he's way too frail. He has 4MSS, loses to certain threats depending on coverage. His STABs aren't the greatest, he doesn't have great resistances, his speed is subpar, and his priority sucks. His strength is his only redeeming factor, and you're wasting a mega over this too. His frailty puts a general pressure on your team to bring him in safely, and running mega medicham is just generally not worth it.
He should stay wherever he is, and not rise anywhere near A-