
The best moveset for Mamoswine in the current competitive meta typically features the moves Ice Shard, Protect, Icicle Crash, Earthquake.
In the Pokémon Champions meta, Mamoswine can be countered by exploiting its weaknesses (fighting 2x, fire 2x, grass 2x, steel 2x, water 2x) and using effective check/counter teams.
The best item for Mamoswine is typically Focus Sash, based on high-level tournament and ladder stats.