The [Kuva Nukor] which can melt everything down to its tiny bits!

A Riven isn't necessary in this case, as DE nerfed it to oblivion.
I am combining just because of the reason, that I am able to get a second element with it, Heat Damage.

I personally am using a Viral (Regular) + Heat (Riven) build, which is even more powerful.
It is up to you, what you wanna use on the Riven-Slot.

Updated for the newest Galv-Mods.
Primed [Serration] is not necessary anymore. You are better off using Galv Shot in this case, other than that, you could still replace [Lethal Torrent] with (Primed) [Serration] for a higher damage output, but you will melt away your enemies easily anyways.