As a note: Latias can beat Yveltal should it carry one of Ice Beam, Thunderbolt, or Draco Meteor in its fourth slot, so it's far from a counter. If you want a counter, Unaware Normalceus or Chansey, Standard Aegislash, and Tyranitar are probably the best options. Admittedly it does beat, say, stored power+Dragon pulse, but that's both risky with rocks and somewhat suboptimal.