Thundurus (Therian Forme)

Thundurus Therian Forme boasts considerably more ATK than its Incarnate variant, and combined with a stronger PvE moveset, is a great Electric-type attacker for raids and gyms. Unfortunately its poor DEF and STA stats causes it to faint rather quickly compared other attackers, and its Flying sub-typing can sometimes be a liability against Ice-type attacks that Water Pokemon typically have.

Access to Wildbolt Storm has improved its performance, granting it a DPS that rivals some other top Electric attackers. This makes Thundurus Therian generally worth running. However, Thundurus's frailty, Wildbolt Storm's 1-bar cost, and Volt Switch's long duration can make the Pokemon feel rather clunky to use.

Best PvE Offensive Moveset

• Volt Switch is the fast move of choice since it benefits from STAB and suits Thundurus's role.
• Bite has no use for an Electric/Flying Pokemon.
• Wildbolt Storm* is Thundurus's best Electric charged attack.
• Thunderbolt can be used if Wildbolt Storm is unavailable, or as a second charged attack for consistency as it is Thundurus's only 2-bar move.
• Thunder falls behind in performance considerably.
• Sludge Wave and Focus Blast don't synergize with Thundurus.

Volt Switch has decent damage output backed by STAB, and provides double the energy generation that Bite offers. 

Wildbolt Storm is by far and away Thundurus's cheapest charged attack; it also benefits from STAB and applies a useful Attack debuff on the target. Thunderbolt and Thunder are both outclassed as Electric-type options due to their expensive cost. Sludge Wave doesn't synergize well for an Electric/Flying Pokemon, and requires a lot of energy to use. Focus Blast is recommended for its wide coverage, but while it does demand the most amount of energy, other options don't provide as much value for their costs.