Shadow Dragonair

Dragonair isn't a great Pokemon now per-say, but it will be when it evolves!

Before evolving, check its IVs. If it has low attack but high defense/HP and has a CP that is 1500 or under, maybe think about keeping it and using it in PvP? Dragonair is pretty good in the Go Battle League.

Best PvE Offensive Moveset

• Dragon Breath performs better than Iron Tail on offense. 
• Dragon Pulse pairs well with Dragon Breath and also benefits from STAB. 
• Aqua Tail and Wrap offer quick damage with slightly less energy cost, but are inferior otherwise. 
• Body Slam is in the same boat, and can't deal Super Effective Damage. 

Best PvE Defensive Moveset

• Iron Tail has way more base power and is more suitable for defense. 
• Aqua Tail has the earliest damage window and can be used frequently. 
• Wrap is easier to dodge but performs almost the same as Aqua Tail. 
• Body Slam performs closely with the above, and is a good alternative. 
• Dragon Pulse hits hard, but is easy to dodge and might not even be used before Dragonair faints. 

Dragon Breath + Aqua Tail and Body Slam

Dragon Breath is the best fast move on Dragonair, featuring superior DPT (Damage Per Turn), EPT (Energy Per Turn), and also benefiting from STAB. 

Aqua Tail is almost always preferred on Dragonair since it is among the lowest energy-demanding charge moves. Body Slam is now a strong option for dealing solid neutral damage, and its low energy cost allows it to be spammed frequently. This makes Wrap redundant. Dragon Pulse has an unexciting 1.5 DPE (Damage Per Energy) and costs 60 energy to use, but if unshielded can KO opposing Dragon-types or severely injure most other Pokemon in Great League. 

Great League: 4 / 5

Jack of all trades, master of none. Dragonair gained some fame during Kingdom Cup in April 2019, where its access to the powerful Dragon Breath allowed it to be a viable option, especially as a lead. While able to serve as a solid generalist, Dragonair faces tough competition from other Dragon-types in Great League, namely Altaria but does offer its own set of strengths. Dragonair has a lot of favorable matchups, but its lack of crushing wins and a relatively lower bulk that prevents it from enduring prolonged fights or sweeping, keep it from emerging as better option in open Great League.   

Ultra League: 0 / 5

With a maximum CP of 2012, Dragonair is only serviceable in Great League. 

Master League 0 / 5

A lot of Dragon-types compete in the Master League. Dragonair ain't one of them though.