Note: this assumes Rocks are up (unless switch-in has a set with Boots or is Hattrem) and Gallade is forcing a switch. If this is unrealistic to you, please tell me.
A-Ranks
252+ Atk Muscle Band Gallade Thunder Punch vs. 252 HP / 0 Def Charizard: 236-278 (65.5 - 77.2%) -- guaranteed 2HKO
252+ Atk Muscle Band Gallade Shadow Sneak vs. 252 HP / 0 Def Charizard: 63-75 (17.5 - 20.8%) -- possible 5HKO (this shows that defensive Zard dies with minimal chip)
252+ Atk Muscle Band Gallade Leaf Blade vs. 252 HP / 176+ Def Jellicent: 226-266 (55.9 - 65.8%) -- guaranteed 2HKO after Stealth Rock
252+ Atk Muscle Band Gallade Psycho Cut vs. 252 HP / 176+ Def Jellicent: 132-156 (32.6 - 38.6%) -- guaranteed OHKO (if Cursed Body procs then it dies after Rocks if Colbur, if it doesn't then it dies even if it's Boots)
252+ Atk Muscle Band Gallade Knock Off (97.5 BP) vs. 252 HP / 4 Def Colbur Berry Mesprit: 119-141 (32.6 - 38.7%) -- guaranteed 3HKO after Stealth Rock
252+ Atk Muscle Band Gallade Knock Off vs. 252 HP / 4 Def Mesprit: 158-188 (43.4 - 51.6%) -- guaranteed OHKO after Stealth Rock (switches in once, dies on next switch-in)
252+ Atk Muscle Band Gallade Close Combat vs. 252 HP / 172+ Def Sandaconda: 151-178 (43.3 - 51.1%) -- 55.5% chance to 2HKO after Stealth Rock (roll in your favor, much more favorable if Spikes are up, odds for Lefties are 5% but they're not that common on SR sets)
252+ Atk Muscle Band Gallade Psycho Cut vs. 0 HP / 0 Def Silvally-Ghost: 141-166 (42.5 - 50.1%) -- 91.8% chance to 2HKO after Stealth Rock
252+ Atk Muscle Band Gallade Shadow Sneak vs. 0 HP / 0 Def Silvally-Ghost: 108-128 (32.6 - 38.6%) -- guaranteed 2HKO (can come in once with Rocks up if need be, but dies if Spikes are up or 2 turns of Sand chip was taken)
252+ Atk Muscle Band Gallade Close Combat vs. 252 HP / 252+ Def Quagsire: 184-217 (46.7 - 55%) -- 69.1% chance to 2HKO (nice)
252+ Atk Muscle Band Gallade Leaf Blade vs. 252 HP / 252+ Def Quagsire: 368-436 (93.4 - 110.6%) -- 62.5% chance to OHKO (more consistent, but not always run)
252+ Atk Muscle Band Gallade Psycho Cut vs. 252 HP / 80 Def Silvally-Fairy: 129-153 (32.7 - 38.8%) -- guaranteed 3HKO after Stealth Rock (only defensive A-Rank that can come in more than once, but lacks recovery outside of cursed RestTalk sets)
B-Ranks
252+ Atk Muscle Band Gallade Knock Off (97.5 BP) vs. 252 HP / 252+ Def Colbur Berry Uxie: 75-89 (21.1 - 25.1%) -- 98.7% chance to 4HKO after Stealth Rock
252+ Atk Muscle Band Gallade Knock Off vs. 252 HP / 252+ Def Uxie: 100-118 (28.2 - 33.3%) -- guaranteed 2HKO after Stealth Rock
252+ Atk Muscle Band Gallade Knock Off vs. +1 252 HP / 252+ Def Uxie: 68-80 (19.2 - 22.5%) -- possible 5HKO (defensive sets can only come in once, Kee Berry sets make mince meat of Gallade unless unlucky crit)
252+ Atk Muscle Band Gallade Psycho Cut vs. 252 HP / 252+ Def Aromatisse: 118-141 (29 - 34.7%) -- 8.5% chance to 3HKO after Stealth Rock and Leftovers recovery
252+ Atk Muscle Band Gallade Psycho Cut vs. 248 HP / 0 Def Aromatisse: 177-208 (43.7 - 51.3%) -- 61.3% chance to 2HKO after Stealth Rock and Leftovers recovery (PhyDef is probably the best MB Gallade counter in the tier, SpDef is a roll in your favor, PhyDef can still lose to a ZHB flinch)
252+ Atk Muscle Band Gallade Knock Off (97.5 BP) vs. 212 HP / 252+ Def Colbur Berry Cofagrigus: 69-82 (22.2 - 26.4%) -- guaranteed 4HKO after Stealth Rock
252+ Atk Muscle Band Gallade Knock Off vs. 212 HP / 252+ Def Cofagrigus: 92-110 (29.6 - 35.4%) -- guaranteed 3HKO after Stealth Rock
252+ Atk Muscle Band Gallade Knock Off vs. +2 212 HP / 252+ Def Cofagrigus: 46-56 (14.8 - 18%) -- possible 5HKO after Stealth Rock
252+ Atk Muscle Band Gallade Psycho Cut vs. 212 HP / 252+ Def Cofagrigus on a critical hit: 114-135 (36.7 - 43.5%) -- guaranteed OHKO (Gallade wins if it gets a Psycho Cut crit on the last turn/ZHB flinch, loses otherwise, you always live one Shadow Ball so you can stay in if need be)
252+ Atk Muscle Band Gallade Close Combat vs. 248 HP / 252+ Def Druddigon: 178-210 (49.8 - 58.8%) -- guaranteed 2HKO after Stealth Rock (you "win", and by that you mean you take it out but take 59% in return)
252+ Atk Muscle Band Gallade Leaf Blade vs. 252 HP / 208+ Def Palossand: 162-192 (43.3 - 51.3%) -- 59% chance to 2HKO after Stealth Rock
252+ Atk Muscle Band Gallade Knock Off (97.5 BP) vs. 252 HP / 208+ Def Colbur Berry Palossand: 87-103 (23.2 - 27.5%) -- 100% chance to 4HKO after Stealth Rock
252+ Atk Muscle Band Gallade Zen Headbutt vs. 252 HP / 208+ Def Palossand: 108-127 (28.8 - 33.9%) -- 17.2% chance to 2HKO
252+ Atk Muscle Band Gallade Knock Off (97.5 BP) vs. 252 HP / 208+ Def Palossand: 174-206 (46.5 - 55%) -- 98.8% chance to 2HKO after Stealth Rock
252+ Atk Muscle Band Gallade Zen Headbutt vs. 252 HP / 208+ Def Palossand: 108-127 (28.8 - 33.9%) -- guaranteed 2HKO (Leaf Blade is a roll in your favor unless Lefties, Knock Off + ZHB has a very small chance to hax Colbur, bigger chance to hax non-Colbur)
252+ Atk Muscle Band Gallade Psycho Cut vs. 252 HP / 0 Def Rotom: 168-198 (55.2 - 65.1%) -- guaranteed 2HKO after Stealth Rock
252+ Atk Muscle Band Gallade Shadow Sneak vs. 252 HP / 0 Def Rotom: 128-152 (42.1 - 50%) -- guaranteed OHKO (dies if Rocks are up, has a very small chance to live if they aren't)
252+ Atk Muscle Band Gallade Close Combat vs. 252 HP / 252+ Def Eviolite Tangela: 102-120 (30.5 - 35.9%) -- guaranteed 3HKO after Stealth Rock
252+ Atk Muscle Band Gallade Close Combat vs. 252 HP / 252+ Def Tangela: 151-178 (45.2 - 53.2%) -- guaranteed 2HKO after Stealth Rock (decent counter, can stall out CC PP with this + a Ghost-type and 50/50s, just don't get Knocked)
252+ Atk Muscle Band Gallade Psycho Cut vs. 252 HP / 252+ Def Eviolite Clefairy: 100-118 (29 - 34.3%) -- 3.7% chance to 3HKO
252+ Atk Muscle Band Gallade Zen Headbutt vs. 252 HP / 252+ Def Eviolite Clefairy: 114-135 (33.1 - 39.2%) -- 99.9% chance to 3HKO
252+ Atk Muscle Band Gallade Psycho Cut vs. 252 HP / 252+ Def Clefairy: 148-175 (43 - 50.8%) -- 3.1% chance to 2HKO
252+ Atk Muscle Band Gallade Zen Headbutt vs. 252 HP / 252+ Def Clefairy: 169-201 (49.1 - 58.4%) -- 98% chance to 2HKO (if you get flinched or Knocked, you're screwed, otherwise a niche but solid pick, also useful to show when the power of ZHB is useful over Psycho Cut avoiding contact punishing stuff like Rocky Helmet)
Calcs are same as Cofagrigus except
252+ Atk Muscle Band Gallade Leaf Blade vs. 252 HP / 252+ Def Runerigus: 128-152 (40 - 47.5%) -- guaranteed 3HKO after Stealth Rock and Leftovers recovery
252+ Atk Muscle Band Gallade Leaf Blade vs. +2 252 HP / 252+ Def Runerigus: 66-78 (20.6 - 24.3%) -- possible 5HKO after Stealth Rock and Leftovers recovery
252+ Atk Muscle Band Gallade Leaf Blade vs. +2 252 HP / 252+ Def Runerigus: 66-78 (20.6 - 24.3%) -- guaranteed 2HKO after Leftovers recovery (better hope Leaf Blade doesn't crit, which it has a 1/3 chance to do, and increases if you click Rest on the third turn)
C-Ranks
252+ Atk Muscle Band Gallade Zen Headbutt vs. 252 HP / 252+ Def Alcremie: 133-157 (39.8 - 47%) -- 36.3% chance to 2HKO after Stealth Rock
252+ Atk Muscle Band Gallade Psycho Cut vs. 252 HP / 252+ Def Alcremie on a critical hit: 175-207 (52.3 - 61.9%) -- guaranteed 2HKO (ZHB is a roll not in your favor, Psycho Cut can theoretically fish for the double crit but Alcremie wins otherwise)
252+ Atk Muscle Band Gallade Zen Headbutt vs. 252 HP / 64 Def Altaria: 157-186 (44.3 - 52.5%) -- 19.9% chance to 2HKO
252+ Atk Muscle Band Gallade Psycho Cut vs. 252 HP / 64 Def Altaria: 136-162 (38.4 - 45.7%) -- guaranteed 3HKO (ZHB sorta beats it in the sense that Altaria is forced to Roost or else it gets too low, so you can eventually get the flinch, but it's unreliable, Psycho Cut can't break it)
252+ Atk Muscle Band Gallade Close Combat vs. 252 HP / 252+ Def Appletun: 192-226 (45.2 - 53.3%) -- 33.6% chance to 2HKO (was surprised by this one, anything that isn't max/max loses btw)
252+ Atk Muscle Band Gallade Close Combat vs. 252 HP / 4 Def Carbink: 162-192 (53.2 - 63.1%) -- guaranteed 2HKO after Leftovers recovery
252+ Atk Muscle Band Gallade Close Combat vs. 252 HP / 252+ Def Carbink: 124-147 (40.7 - 48.3%) -- guaranteed 3HKO after Leftovers recovery (never seen a PhyDef Carbink, theoretically it switches in and does over half with Body Press if Gallade is -2 or Toxics it, but lacks reliable recovery)
252+ Atk Muscle Band Gallade Leaf Blade vs. 252 HP / 240+ Def Claydol: 162-192 (50 - 59.2%) -- guaranteed 2HKO after Stealth Rock and Leftovers recovery
252+ Atk Muscle Band Gallade Knock Off (97.5 BP) vs. 252 HP / 240+ Def Colbur Berry Claydol: 88-104 (27.1 - 32%) -- 1.9% chance to 3HKO after Stealth Rock
252+ Atk Muscle Band Gallade Knock Off vs. 252 HP / 240+ Def Claydol: 116-138 (35.8 - 42.5%) -- guaranteed 2HKO (Leaf Blade beats it, Claydol can switch into Knock Off once but not again)
252+ Atk Muscle Band Gallade Close Combat vs. 252 HP / 252+ Def Eldegoss: 178-210 (54.9 - 64.8%) -- guaranteed 2HKO
252+ Atk Muscle Band Gallade Psycho Cut vs. 252 HP / 252+ Def Eldegoss: 103-123 (31.7 - 37.9%) -- 92.6% chance to 3HKO (worse Tangela but this + a Fighting resist with recovery can force Gallade to predict properly, non-Boots gets outdamaged by Rocks + Psycho Cut)
252+ Atk Muscle Band Gallade Knock Off (97.5 BP) vs. 252 HP / 244+ Def Eviolite Hattrem: 158-188 (49.6 - 59.1%) -- 99.6% chance to 2HKO (very, very high chance for Gallade to win)
252+ Atk Muscle Band Gallade Close Combat vs. 252 HP / 252+ Def Pyukumuku: 138-163 (43.9 - 51.9%) -- 73% chance to 2HKO after Stealth Rock and Leftovers recovery
252+ Atk Muscle Band Gallade Close Combat vs. 252 HP / 252+ Def Pyukumuku: 138-163 (43.9 - 51.9%) -- 11.7% chance to 2HKO (another solid counter, but only used on some stalls + niche balances)
I believe I was through with these calcs. If you think I'm missing anything, tell me.