Here are some calcs of Specs Goodra against the bulkiest special walls:
252+ SpA Choice Specs Latias Draco Meteor vs. 252 HP / 252+ SpD Hippowdon: 274-324 (65.23 - 77.14%)
252+ SpA Choice Specs Latias Draco Meteor vs. 252 HP / 252+ SpD Jellicent: 217-256 (53.71 - 63.36%)
252+ SpA Choice Specs Latias Draco Meteor vs. 252 HP / 172+ SpD Gastrodon: 274-324 (64.31 - 76.05%)
252+ SpA Choice Specs Latias Draco Meteor vs. 248 HP / 0 SpD Tentacruel: 265-313 (73 - 86.22%) -- guaranteed 2HKO
252+ SpA Choice Specs Latias Draco Meteor vs. 248 HP / 0 SpD Vaporeon: 324-382 (69.97 - 82.5%) -- guaranteed 2HKO after Stealth Rock
252+ SpA Choice Specs Latias Fire Blast vs. 252 HP / 236+ SpD Celebi: 256-302 (63.36 - 74.75%) -- guaranteed 2HKO
252+ SpA Choice Specs Latias Fire Blast vs. 252 HP / 236+ SpD Jirachi: 256-302 (63.36 - 74.75%) -- guaranteed 2HKO
252+ SpA Choice Specs Latias Focus Blast vs. 248 HP / 252+ SpD Heatran: 264-312 (68.57 - 81.03%) -- guaranteed 2HKO
252+ SpA Choice Specs Latias Focus Blast vs. +1 252 HP / 252+ SpD Tyranitar in sand: 248-292 (61.38 - 72.27%) -- guaranteed 2HKO
252+ SpA Choice Specs Latias Sludge Bomb vs. 252 HP / 252+ SpD Sylveon: 172-204 (43.65 - 51.77%) -- 74.22% chance to 2HKO after Stealth Rock
This means only Jellicent and Chansey/Blissey can survive 2 attacks from specs Goodra. This makes Goodra a fantastic specs user, with max HP investment and it's great special bulk you can easily switch in on electric, grass, fire and water attacks, and fire off power attacks. You might think Specs Goodra is outclassed by Hydreigon or Latios/Latias, but Goodra doesn't have Hydreigons garbage dark typing and has way more special bulk. What Goodra has over Latios/Latias is a way better movepool (Focus Blast, Fire Blast and Sludge Bomb). Goodra also isn't pursuit weak like Latias/Latios.
252+ SpA Choice Specs Latias Draco Meteor vs. 252 HP / 252+ SpD Hippowdon: 274-324 (65.23 - 77.14%)
252+ SpA Choice Specs Latias Draco Meteor vs. 252 HP / 252+ SpD Jellicent: 217-256 (53.71 - 63.36%)
252+ SpA Choice Specs Latias Draco Meteor vs. 252 HP / 172+ SpD Gastrodon: 274-324 (64.31 - 76.05%)
252+ SpA Choice Specs Latias Draco Meteor vs. 248 HP / 0 SpD Tentacruel: 265-313 (73 - 86.22%) -- guaranteed 2HKO
252+ SpA Choice Specs Latias Draco Meteor vs. 248 HP / 0 SpD Vaporeon: 324-382 (69.97 - 82.5%) -- guaranteed 2HKO after Stealth Rock
252+ SpA Choice Specs Latias Fire Blast vs. 252 HP / 236+ SpD Celebi: 256-302 (63.36 - 74.75%) -- guaranteed 2HKO
252+ SpA Choice Specs Latias Fire Blast vs. 252 HP / 236+ SpD Jirachi: 256-302 (63.36 - 74.75%) -- guaranteed 2HKO
252+ SpA Choice Specs Latias Focus Blast vs. 248 HP / 252+ SpD Heatran: 264-312 (68.57 - 81.03%) -- guaranteed 2HKO
252+ SpA Choice Specs Latias Focus Blast vs. +1 252 HP / 252+ SpD Tyranitar in sand: 248-292 (61.38 - 72.27%) -- guaranteed 2HKO
252+ SpA Choice Specs Latias Sludge Bomb vs. 252 HP / 252+ SpD Sylveon: 172-204 (43.65 - 51.77%) -- 74.22% chance to 2HKO after Stealth Rock
This means only Jellicent and Chansey/Blissey can survive 2 attacks from specs Goodra. This makes Goodra a fantastic specs user, with max HP investment and it's great special bulk you can easily switch in on electric, grass, fire and water attacks, and fire off power attacks. You might think Specs Goodra is outclassed by Hydreigon or Latios/Latias, but Goodra doesn't have Hydreigons garbage dark typing and has way more special bulk. What Goodra has over Latios/Latias is a way better movepool (Focus Blast, Fire Blast and Sludge Bomb). Goodra also isn't pursuit weak like Latias/Latios.