the game doesnt matter because I own all the games with goodra in it
The best odds come from Legends: Arceus, (unsurprisingly,) at a grand total of 1/128. These odds come from having Shiny Charm, a perfect Dex entry, and a Normal Mass Outbreak.
If you lack a Perfect Dex entry, odds go to 1/137. If you lack both Perfect Dex entry and Shiny Charm, odds are 1/141, as long as you have Dex level 10.
All of these odds are far better than anything else you can find in any other game, so I recommend this as your method.
Hope I could help