Tyranitar @ Assault Vest
Ability: Sand Stream
EVs: 248 HP / 8 Atk / 252 SpD
- Stone edge
This Tyranitar can reliably switch in on any of Charizard Y's attacks, overwrite the sun, take a second hit and knock out Charizard Y with Stone Edge. Even Charizard Y with Earthquake can't do much.
252 SpA Mega Charizard Y Solar Beam (60 BP) vs. 248 HP / 252+ SpD Assault Vest Tyranitar in Sand: 50-60 (12.4 - 14.8%) -- possible 7HKO
And in the sun, if for some ungodly reason that happens.
252 SpA Mega Charizard Y Solar Beam vs. 248 HP / 252+ SpD Assault Vest Tyranitar: 146-174 (36.2 - 43.1%) -- guaranteed 3HKO
And the Earthquake variants.
4 Atk Mega Charizard Y Earthquake vs. 248 HP / 0 Def Tyranitar: 138-164 (34.2 - 40.6%) -- guaranteed 3HKO
And the weird Dragon Dance Charizard Ys
+1 4 Atk Mega Charizard Y Earthquake vs. 248 HP / 0 Def Tyranitar: 206-244 (51.1 - 60.5%) -- guaranteed 2HKO
Pretty much the only way Charizard Y could reliably take out Tyranitar is by running 232 attack ivs, get a Dragon dance off and have rocks and 3 layers of spikes up when the max health Tyranitar switches in.¨
Edit: I just tought to add that since Tyranitar has no way of recovering hp himself, it could be very beneficial running something with wish support, like Togekiss for example. Togekiss also compliments some of Tyranitar's weaknesses and can also help dealing with Charizard X.