Mega Beedrill

One of the first Mega Pokemon introduced to Pokemon Go, Mega Beedrill looks absolutely terrifying with its high ATK stat. While Bug and Poison typings are typically not as valuable as other typings, the early accessibility makes it a good entry option. It should be noted while Mega Beedrill packs a big punch (or sting), it's also very fragile and likely won't last long as an attacker. Stronger Bug-type Mega Pokemon will likely be introduced in the future to replace Mega Beedrill, but for now this is a cool addition to any player's collection. Also worth noting is that Mega Beedrill packs the highest Poison DPS of any of the Mega Evolutions, though Poison is still a less than useful type in raids generally speaking.

Best PvE Offensive Moveset

• Bug Bite* and Infestation have roughly similar performance, with Infestation having better damage and Bug Bite better energy gain, though the legacy Bug Bite pulls ahead just slightly. 
• Poison Jab is good when paired with Sludge Bomb, though Sludge Bomb pairs with Bug Bite for Beedrill's highest performance against grass types and neutral targets.
• X-Scissor is fast and furious, giving Beedrill a bug type set.
• Aerial Ace is fairly slow, but if you've just started and are desperate for fighting-type counters, you can leverage Beedrill's double fighting-resistance and use this. However, even many neutral matchups can out-damage Beedrill on this metric.
• Fell Stinger has a higher attack rating than X-Scissor, but it's substantially slower which makes it weaker in practice.
• Beedrill is a bad Bug-type attacker. It's an even worse Ground-type. Leave Drill Run alone.