Garchomp

Garchomp is perhaps one of the most anticipated non legendary Pokemon of Gen 4, and those who grew up with the main series games vividly remember fighting it (and maybe using it). Does Garchomp leave a similar impression on Pokemon GO? Well it's still certainly a menacing Pokemon. As a Dragon-type attacker, it is a fairly solid choice, although the competition is large and Garchomp does not have the highest ATK stat. In that role, Garchomp sets itself apart due to the different resistances provided by its secondary Ground-type, and may find itself shining against Dragon-type bosses that carry Rock- or Electric-type moves.

The Gible Community Day in June 2021 gave Garchomp Earth Power, slightly buffing its already solid Ground attacking capabilities. Garchomp is now one of the best Ground-type attackers in the game. With awesome stats and useful resistances (especially that near immunity to Electric-type attacks), Garchomp will surely dominate bosses where Ground-type attacks are the best choice. Unfortunately, the generally low DPS of Ground-type attacks often means that other types are better attacking choices, meaning that Garchomp will have to rely on Sunny or Clear weather to truly stand out.

Best PvE Offensive Moveset

• Dragon Tail should be paired with Outrage for the flagship Dragon-type moveset.
• Mud Shot is recommended if Garchomp is to be used as a Ground-type attacker.
• Earth Power* is better than Earthquake for PvE offense, but is more limited in accessibility. 
• Fire Blast and Sand Tomb have no offensive relevance.

Best PvE Defensive Moveset

• Dragon Tail does thrice as much damage per hit as Mud Shot.
• Outrage is Garchomp's best 2-bar charged move. At least this can keep the attacker honest.
• Sand Tomb has the advantages of being off-type with Dragon Tail and harder than the other options to dodge, but it's not very strong.
• Earth Power* hits quite hard, but its long animation speed is easily dodged. 
• Earthquake and Fire Blast are both 1-bar charged moves that are extremely easy to dodge.

Garchomp has two distinct playstyles based on its fast move:

Dragon Tail is a solid move thanks to the GBL Season 8 update, and provides Garchomp with a significant amount of fast move pressure, contrasting the charge move focus of the previous moveset. Sand Tomb is a necessary complementary move - not only for its low cost, but also because the Defense drop immediately benefits Dragon Tail. Outrage can be used to nail Flying types so that Garchomp isn't entirely reliant on Dragon Tail to dent them, but Earth Power can dent Zacian, Xerneas, Primarina, and burst down Steel types. Earthquake and Fire Blast are costly options that are comparatively unreliable because of Dragon Tail's average energy gain.

Mud Shot’s fantastic energy gain combined with two very powerful (but expensive) charged moves in Earth Power and Outrage make Garchomp a terrifying threat. It is at its best when the opponent has no shields, so it should be saved until the end of a game as a closer. Notably, though, you can exchange Earth Power out for Sand Tomb, trading some of that incredible nuke potential for the ability to actually perform while shields are up. Earthquake is stronger than Earth Power and has higher Damage Per Energy, but Earth Power is preferred for its lower cost. Fire Blast is largely inefficient and outclassed, although it can deal significant damage to Togekiss. Do not use mono-Ground Garchomp.