When your Attack Damage is lower than the Beetles Damage Reduction:
The Beetle will be listed as impossible, take some time to add to your AD and you will not have this problem anymore.
I believe that the beetle's DR is 9, so your AD needs to be 10 or more to deal damage.
I suggest 2X Villain's ring from store, there the best unless you want to grind for ever.
Villain's ring are better than pure +6 AD ring, since you will get +50 AC also from V rings, and damage alone is no good when you miss.
L37 Naked: 86hp, 10 AP, AC 125, AD 22, 2.5k gp
Gear: HP 102, AC 259, 12AP, Dam 6X 28-34, BC 12, DR 1
Skills:40-44 evasion or weapons, 50 Fortitude 4, 54,58,62 F5 65
QS dag, Rem C V, E C Helm, Vacor's B, Marrow, Villain's ring 2X, L G attack, Rem Shield
I suggest 2X Villain's ring from store, there the best unless you want to grind for ever.
Villain's ring are better than pure +6 AD ring, since you will get +50 AC also from V rings, and damage alone is no good when you miss.
The Villain's ring would be my reccomendation as well, they are not too expencive and are easy to get to early on in the game.
The Ring of Damage +6 is pretty far away for a new players to get to now. They used to be in the starting town, now they are not.