About to fight Viper Kodachi, any ideas for a good thunder weapon?

[worm on a sidewalk]

Preferably bow, long sword, or dual blades. Something that can last moreso

[lexilogo]

You don't need a thunder weapon if you're using a Longsword.

In any case, Bone/Ore trees are probably the best overall choices at that early point in the MR campaign. (incidentally, Viper Kadachi is a very good Longsword) However, if you really want to grind for good Thunder weapons go for Tobi-Kadachi ones. I don't know if the Bow or DB are that great overall (and IIRC their sharpness is sub-par) but they do have very high Thunder so they should rip through Viper.

[AetherLiger]

Kadachi Strike Bow and Antidote decos

[Nope]

You'll be fine without thunder weapons (though you'll if you use bow) I even use Defender longsword till I switch to tigrex
Just slot in poision resist 3 decos and you're gold

[DaBa]

No need to tailor make your weapon for an early monster, just go with anything that has good raw. You can worry about elemental weaknesses once you get to the end game.

[gachi is manly]

Hell I was still using rarity 8 HR weapons when I killed him.

Pretty sure I was using Taroth Glaive Ice. Definitely don't need to go out of your way to find an element early monsters are weak against.

[Aurora]

I used Defender weapons until velkhana with no issues

[DaBa]

Originally posted by Aurora:

I used Defender weapons until velkhana with no issues

That was me as well. They are so good that there's no reason to upgrade until you get access to the final upgrades (rarity 10) of some of the basic monster's weapons. Kulu tree final weapons are particularly good for how early you can get access to them. Great Jagras is decent as well. They are good enough to finish the story, and then get replaced by others.