Monster no Goshujin-sama - Vol. 7 Ch. 34.1

[MangaDex]

 

[BadHaremSchollar]

Sound weird. But an arachne is kind of a really mobile cavalry.

Try javelins or any throwing weapon.

 

[Otherworlder]

Crossbows would also be a good choice for her. She's strong enough to span even a heavy one just by pulling the string back, and a crossbow has more power, accuracy, and range than any hurled weapon. They make barrelled crossbows that can keep a bolt in place even when she's hanging from the ceiling.