The user gets all the party Pokémon to attack the foe. The more party Pokémon, the more damage.
Effect
this move has the following additional effects:
Hits X times in a row, where X is 1 (the user) plus the number of Pokémon in the user's party (both user's and partner's parties in double battles) which are unfainted, have no status problems and isn't the user. The base power of each hit is 5 + Y/10, where Y is the base Attack stat for the species of the corresponding suitable Pokémon. Beat Up's user is still the one performing the hits; there is nothing special about damage calculation.
Pokémon that learn Necromancy
Level Up
Note: Due to memory issues, results are limited to 50.