Mega Gengar is weak to Ground, Ghost, Psychic, and Dark type attacks in the main games and in Pokémon GO.

What Is Mega Gengar Weak Against? (Quick Scoop)

Mega Gengar keeps Gengar’s dual Ghost/Poison typing, which gives it four clear type weaknesses.

Main Type Weaknesses

Mega Gengar takes super-effective damage from:

  • Ground-type moves (like Earthquake, Earth Power).
  • Ghost-type moves (like Shadow Ball, Shadow Claw, Shadow Punch).
  • Psychic-type moves (like Psychic, Psyshock, Confusion).
  • Dark-type moves (like Crunch, Dark Pulse, Knock Off).

In Pokémon GO, these same four types are explicitly listed as Mega Gengar’s weaknesses.

Example Counters People Use

Players often recommend strong Psychic and Ghost attackers to exploit those weaknesses.

Some commonly mentioned counters include:

  • Powerful Psychic attackers like Mewtwo, Alakazam, Espeon, Gardevoir, and Gallade.
  • Strong Ghost attackers using Shadow-type moves to hit that Ghost weakness.
  • Ground and Dark types with high attack stats to punish Mega Gengar’s low bulk.

In forum-style discussions and raid guides, people consistently highlight that Mega Gengar hits very hard but is quite frail, so exploiting these four weaknesses lets you bring it down fast.

Extra Notes & “Latest” Context

  • Official Pokédex-style entries and GO databases still show Mega Gengar as Ghost/Poison with weaknesses to Ground, Psychic, Ghost, and Dark.
  • Recent raid guides and tools for Pokémon GO emphasize these same four weaknesses when suggesting best counters and teams.

TL;DR:
If you’re asking “what is Mega Gengar weak against,” hit it with Ground, Ghost, Psychic, or Dark moves, and you’ll be taking full advantage of its typing and relatively low defenses.

Information gathered from public forums or data available on the internet and portrayed here.