The best moveset for Orthworm in the current competitive meta typically features the moves Shed Tail, Body Press, Heavy Slam, Protect.
In the Pokémon Champions meta, Orthworm can be countered by exploiting its weaknesses (fighting 2x, fire 2x, ground 2x) and using effective check/counter teams.
The best item for Orthworm is typically Sitrus Berry, based on high-level tournament and ladder stats.