
fast sub (Charizard-Mega-Y) @ Charizardite Y
Ability: Blaze
EVs: 16 HP / 240 SpA / 252 Spe
Timid Nature
IVs: 0 Atk
- Blast Burn
- Solar Beam
- Air Slash
- Substitute
Seismic Toss vs. 16 HP Charizard-Mega-Y: 100-100 (33.2 - 33.2%) -- guaranteed 4HKO

def sub (Charizard-Mega-Y) @ Charizardite Y
Ability: Blaze
EVs: 16 HP / 120 Def / 180 SpA / 192 Spe
Timid Nature
IVs: 0 Atk
- Blast Burn
- Solar Beam
- Air Slash
- Substitute
+1 252+ Atk Mold Breaker Gyarados-Mega Waterfall vs. 16 HP / 120 Def Charizard-Mega-Y in Sun: 258-306 (85.7 - 101.6%) -- 6.3% chance to OHKO

spdef sub (Charizard-Mega-Y) @ Charizardite Y
Ability: Blaze
EVs: 240 HP / 4 SpA / 80 SpD / 184 Spe
Timid Nature
IVs: 0 Atk
- Blast Burn
- Solar Beam
- Air Slash
- Substitute
252+ SpA Adaptability Porygon-Z Hyper Beam vs. 240 HP / 80 SpD Charizard-Mega-Y: 306-360 (85.7 - 100.8%) -- 6.3% chance to OHKO
252+ SpA Choice Specs Greninja Hydro Cannon vs. 240 HP / 80 SpD Charizard-Mega-Y in Sun: 282-332 (78.9 - 92.9%) -- guaranteed 2HKO
The combination of Substitute and Air Slash allow Charizard Y to bypass its most direct counters a majority of the time. Stone Edge and Head Smash have 80% accuracy. Slow choice band rock types need to land five attacks (one for each sub, plus one for the last 1 hp) and avoid the Air Slash flinch on turn 5.
.8 ^ 5 * .7 = 0.22937 = 22.94%
Sub Air Slash Charizard Y beats slow choiced Stone Edge users 77.06% of the time. If the opponent isn't choiced and doesn't need to land the fifth rock attack, their odds increase to .8 ^ 4 * .7 = 0.28672 = 28.67%.
Let's look at some higher accuracy rock attacks. Rock Slide is a viable option to hit Sub Charizard more reliably, in theory.
.9 ^ 5 * .7 = 0.41334 = 41.33%
Charizard Y is still winning an uncomfortable 58.67% of the time. Let's check again without a choice item (4 attacks vs subs): .9 ^ 4 * .7 = 0.45927 = 45.93%. Still losing for the rock type.
Let's go out of our way and run Rock Tomb with 95% accuracy.
.95 ^ 5 * .7 = 0.54165
The Rock Tomb user is finally winning a slim majority of the time. Let's add a perfect accuracy move to turn 5: .95 ^ 4 * .7 = 0.57015 = 57.02%
Even with every stop pulled out, slow rocks struggle to get barely better than coinflip odds vs Charizard Y. I will point out that fast rock attackers (Terrakion, Archeops, Mega Diancie, Mega Aerodactyl, Scarf Stone Edge Kyurem-B, DD Stone Edge Mega Gyarados) do beat Charizard Y 80% of the time, which is what most players are used to.
I'm kind of ignoring a lot of other things Charizard Y does and focusing on the fact that
with minimal opportunity cost, Charizard Y is beating its most direct counters a majority of the time. Charizard Y is an unhealthy and uncomfortably RNG-based element in the metagame.
...many Stone Edge & Rock Slide users outspeed Charizard (some with scarf). The calculations don't tell the whole story, but they are a step less abstract than a rock png. I was mostly hoping to demonstrate the zard y problem being deeper than "run a rock type lol."
Charizard Y flinches through its checks, meaning the worse player can get bailed and win.
Charizard Y also misses its imperfect accuracy STABs, meaning that once again the worse player can get bailed and win.
The goal is 'to create a metagame that is conducive to the more "skilled" player winning over the less "skilled" player a majority of the time...' Charizard Y does not fit with this philosophy.