Mega Sceptile

Yes, this is the Grass Type Mega Evolution that you've been looking for.

Mega Sceptile is a massively powerful force in Pokemon Go. It has incredible Grass Type damage that allows for very little competition, and a sub-typing that frequently gives it a double-resistance in relevant raids... unless your target happens to have an Ice Type coverage move. While it does face some competition, this is definitely one of the apex Mega Evolutions, and should be a staple in everyone's team.

Best PvE Offensive Moveset

• Bullet Seed should be paired with Frenzy Plant* if possible for maximum damage and Grass-type DPS.
• Leaf Blade is a good alternative, but it is a bit behind.
• Fury Cutter is viable, as it outperforms Bullet Seed when both hit for the same level of effectiveness. It can even be viable when not Super Effective due to its high energy gains.
• Earthquake, Aerial Ace, Breaking Swipe, and Dragon Claw don't perform as well, and all but the latter two lack STAB.