In Pokémon, Dark and Ghost type moves are strong against Ghost-type Pokémon.

Ghost type weaknesses

  • Ghost-type Pokémon take super-effective damage from Dark-type moves.
  • They also take super-effective damage from Ghost-type moves.

So if you want to counter a Ghost-type, using Dark Pokémon (or anything that knows strong Dark moves) is usually the safest play.

Extra matchup tips

  • Ghost-types are immune to Normal and Fighting moves, so avoid relying on those.
  • Common strong counters include Dark-type attackers like Tyranitar, Hydreigon, and Darkrai in games where they are available.

In short: bring Dark moves first, Ghost moves second, and skip Normal/Fighting when facing Ghosts.

TL;DR: What is strong against Ghost type?
Use Dark and Ghost moves; avoid Normal and Fighting against them.

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