I know this will get a fair amount of debate, but I'll try my hand at nominating Charizard for A-Rank. Don't get me wrong, that SR weakness is still there, but if Moltres had no problems getting to S-Rank, this shouldn't be enough to hold Charizard in B-Rank imo.
Stealth Rock and lack of priority are pretty much the only flaws I see in Charizard. Other than that, Charizard's power, coverage, and even reasonably acceptable bulk for a sweeper are downright fantastic and well worth it. Sure, Charizard wants Rapid Spin support to function at his best, but he doesn't need it, a Stealth Rock preventer in Sawk or Golurk functions just fine. Now let's worry about what happens if Charizard gets in. Charizard has the deadly combination of power, coverage and speed all wrapped up in a nice fire-breathing dragon package, in other words an absolute nightmare to switch into. Fire and Flying STABs speak for themselves in this meta, striking down a huge variety of pokemon hard. To add to that, Charizard has access to moves like Focus Blast, Hidden Power Grass/Solarbeam and Dragon Pulse, meaning would be checks in Lickilicky, Seismitoad, Golem and Altaria risk being annihilated. Flareon and Mantine, and to an extent Grumpig (succumbs to Solar Power Zard) and Munchlax (dislikes Focus Blasts) are pretty much the only safe switch-ins to a Special Charizard.
LO Charizard boasts incredible power, able to 2HKO max HP Musharna after Lefties provided Calm Mind has not been used. He can preserve his health with Roost, meaning his matchup against Will-o-Wisp users, such as Weezing and Misdreavus, that he can switch in on is made that much easier. The Stealth Rock weakness isn't so bad when you consider Charizard can either Roost the damage away or go for a Blaze-boosted Fire Blast, and nothing short of Flash Fire or bulky Thick Fat pokemon would appreciate that much at all. Sunny Zard can crack massive holes in stall teams, with utterly insane firepower to tear its targets a new one, and Solarbeam everything else that stands in its path. This is a threat you want to kill immediately, and that could be easier said than done despite Solar Power's health draining due to Zard's reasonable bulk and Roost.
Charizard is pretty darn fearsome, but does have its fair share of counters and checks, as its power and coverage aren't phenomenal and its speed good but not excellent. Thankfully, Charizard has the tools it needs to bypass its obstacles. There are a good number of special walls that can take on special Charizard, but are scared shitless when they see a Swords Dance as they switch in. Physical Zard has 2 very powerful STAB moves in Flare Blitz and Acrobatics, which can destroy pretty much all of special Zard's counters. Since this Charizard can boost its power without losing health or have a "damage cap" (Special Zard cannot stack any more boosts), it can sweep late game as well by not succumbing to residual damage or simply overpowering its opponent. Charizard has an issue with faster opponents, and its SR weakness only compounds this issue as Charizard would be dead regardless of whether or not it switches (<--undoubtedly people's main gripe with Charizard). Charizard still has options to overcome this issue, the most obvious being a Choice Scarf, which allows Charizard to clean up easily and lessens the risk of being revenge killed. However, Choice Charizard is generally a bad idea due to, again, its SR weakness. However, Charizard can still reduce the revenge-killing risk by resorting to moves. Dragon Dance is a tempting option as it also powers Charizard up, but being illegal with Acrobatics greatly hurts this set's potential. Really your best bets to overcome this problem are Substitute and Talwind. The former combines with Roost to make the famed "SubRoost" set: an absolute pain for defensive teams to take out/status and impossible for offensive teams to revenge kill safely. Tailwind take sit up a notch, which at the cost of only lasting only 3 usable turns, a preparation turn, and a moveslot, grants it more speed and versatality (able to switch moves) than Scarf Charizard.
Charizard is a force to be reckoned with, and setting up Stealth Rock is usually only half the trouble of dealing with a well-played Charizard. Its presence has become more notable in Stage 9 due to its notable coverage and speed, since pokemon commonly used to handle the RU drops (and the RU drops themselves) are ill-eqiupped to take on Zard for the most part, among others. Charizard for A-Rank.
