Altaria

Altaria, the Humming Pokemon, is the showy performer of the Dragon family, not a fighter. Its Attack stat is weak and its Health is middling. This alone makes Dragonite a stronger option on defense than Altaria. 

That said, raising an Altaria isn't a terrible option, as it is set to be a fairly efficent Mega Evolution. While its DPS is absolutely nowhere near the levels of monsters like Mega Rayquaza, it can spread its mega boosts for an extremely long time, which can actually work out better full-team average DPS depending on what its team mates are.

Best PvE Offensive Moveset

• Dragon Breath is the superior fast move of choice for PvE offense.
• Peck isn't particularly strong, but can be chosen for a Flying-type role if stronger Pokemon aren't available. 
• Sky Attack synergizes well for a Flying-type role, and is also the strongest charge move in neutral fights. 
• Dragon Pulse makes Altaria a budget Dragon-type attacker if the player lacks stronger Pokemon. 
• Dazzling Gleam outperforms Moonblast, but both lack STAB. 

Best PvE Defensive Moveset

• Peck is generally preferred on defense due to its higher base power than Dragon Breath. 
• Sky Attack has the shortest damage window, and deals moderate damage as a 2-bar move. 
• Dazzling Gleam lacks STAB but is less likely to be resisted by attackers. 
• Dragon Pulse is easily dodged, and also most likely to be resisted. 
• Moonblast as a 1-bar move might not have a chance to be used before Altaria faints. 

Dragon Breath is one of the strongest Fast Moves in the game, with incredible damage output. This allows Altaria to deal solid damage through shields, while also threatening opponents with charged moves. Peck is underwhelming in both damage output and energy gains. 

Sky Attack is both cheap and hard-hitting, which makes it Altaria’s most-used attack. Moonblast is a move limited to Community Day events and Elite TMs, but deals slightly more damage than Dragon Pulse even when considering STAB, provides the same coverage against Dragon-types, in addition to coverage against Dark-types. Its moderately high energy cost results in less frequent use, and Altaria is largely not dependent on it to see success. Dazzling Gleam is a downgrade due to its higher energy cost and less efficient Damage Per Energy (DPE).