Well, since you asked for it...Now, we are going to discuss about the the rest of C and D ranks, and everything else from the whole list that people want to, so we can deal with questionable rankings such as Thundurus to S and Mega Beedril to B. Hopefully, we can make one last update before the the suspect test of Greninja finishes. Also, merry Christmas and happy holidays guys!
Mega Beedrill for B+
So I'm sure by now we all know that Mega Bee is, in fact, a glass cannon. It hits really hard really fast, but can't take a hit for shit. The greatest thing about Mega Bee however, is that when played right, it doesn't ever need to. The main reason Mega Bee is used, obviously, is its crazy powerful Adaptability U-Turn, which punches massive holes in things and creates momentum for the user of Mega Bee. It can come in after a knockout or a slow switch by Pokemon like Celebi or Rotom and proceed to slowly cripple the opponents team by firing off a Knock Off or Drill Run on a predicted switch-in or U-Turning out to retain momentum. Repeating this process throughout the match will leave the team severely weakened, until finally Mega Bee can seal the deal by cleaning up the remaining scraps with its lighting quick moves. Though bulkier teams can withstand the onslaught fairly well, offensive teams as a whole are absolutely demolished by it. With all this said, what keeps Mega Bee out of the A rankings? Well, let's look at the definition of B rank:
B Rank: Reserved for Pokemon that are great in the OU metagame. These Pokemon have more notable flaws than those above them that affect how they function in the tier. Their positive traits still outshine their negatives, but they require a bit more team support to bring out their full potential.
I feel this description is way more accurate for Mega Beedrill than A rank is. Obviously its most notable flaw has to be its abysmal 65/40/80 bulk that prevents it from switching in on basically anything other than certain Fighting-type or Grass-type moves. Even though it is incredibly quick, that bulk leaves it very vulnerable to priority, as although Talonflame and Azumarill might hesitate to switch into a potential Posion Jab, there isn't anything stopping them from revenge killing Bee with a powerful Brave Bird or Aqua Jet. Finally, Mega Bee does require more team support than most other offensive Megas to work at its maximum potential. Hazard support, of course, is mandatory, as Mega Bee is a hit-and-run Pokemon by nature, meaning it will be switching in and out a lot, and it is vulnerable to both Stealth Rocks and Toxic Spikes. Beyond that, Bee will also want teammates who can help it get in safely, so it is best used on a Volt-Turn team with Pokemon like Magnezone and Celebi to help it retain momentum. These flaws aside though, there is no denying that Mega Bee is one of the most deadly Pokemon in the B rankings.
Due to its ability to effectively dismantle most offensive teams while simultaneously retaining momentum, I believe that Mega Beedrill should be ranked B+.