haunter's best move depends on the Pokemon and skill level but if you really want the answer that is technically right i would say the most powerful and effective one.
It can but you need a move tutor to do that.
Haunter is a ghost type of Pokémon. The last move that it learns in Pokémon LeafGreen version is Mean Look.
In Pokémon Crystal, Haunter learns Hypnosis at level 40. This move allows Haunter to put opponents to sleep, which can be strategically useful in battles. Players can also use TMs to teach Haunter other moves if they prefer different strategies.
Goldbat at lv30'ish And Haunter I recommend Goldbat since it's FAST when a Crobat (lv35). Though Ghastly/Haunter is good as well.
You will need give the move reminder a Heart Scale and have Haunt or Gengar relearn the move, for they can't learn it by leveling up.
haunter has to be traded to evlove haunter evolve into gengar in level 42
OF COURSE!! you'll need to trade an haunter to a friend, and haunter will evolve TO GENGAR
Haunter is a ghost type Pokemon
The pre-evolution of Haunter is Ghastly. To evolve Haunter you must trade it to Friend and have them trade it back.
You'll need to trade for a Haunter in order for it to evolve into Gengar.
Gastly evolves into Haunter at level 25, then trade it and it will evolve again into Gengar.
You trade haunter to get gengar.