General purpose kuva karak build centred around the weapon's crit/status balance.

Below I will describe in detail why everything has been taken, so you can further understand how my modding process works.

The Galvanised mods used are mandatory for the weapon to be useful. As a single target assault rifle with no gimmicks, this is the epitome of "left behind by power crept." In other words, the weapon has been powercrept on very hard, and struggles to compete with the KPM of AoE and multi-target weapons. This leads me on to say that I want to make a small disclaimer for people thinking of using this weapon past level 100 that you NEED to be aiming for headshots. Headshots provide a damage and critical damage boost that is essential for keeping this weapon somewhat relevant. If you don't aim for headshots in higher level gameplay your ttk (time to kill) will be tripled.

Nevertheless, you can push Warframe's equivalent of the Kalashnikov pattern rifle past limits that exceed expectations, much like the Kalashnikov rifles themselves.

For this build specifically, I have opted for corrosive rather than viral for more upfront damage, as corrosive damage has a 75% damage bonus versus ferrite armour, the most common armour type on nearly every grineer unit, plus sentients. Furthermore, the corrosive status will help strip the majority of the armour that you come up against. This is further compounded by the choice of heat progenitor and heat mod, because this will further assist in removing armour, but has a very useful damage bonus against grineer health and infested health. In addition to this, the heat status is a brilliant layer of DoT (damage over time) that CCs (crowd controls) enemies affected by it for a small layer of self peel.

The Weapon itself is mostly slash-based, so on the off chance that your 111% status chance (for each of the 3-4 bullets shot per click) decides to proc slash, this is good. It's another layer of DoT that combines well with heat.

As a crit-viable weapon, it's a no-brainer decision to slap on [Vital Sense] for the massive multiplicative damage boost of crit damage. Crits also bypass a good amount of the game's damage reduction and attenuation buffs on certain bosses.

Lastly for mods we come to the flex slots. In this case, the bane mod is the flex slot. This is the slot that's left for personal preference or situational mods. Personally, I use a riven, as [Kuva Karak] rivens are quite cheap and usually really good. However if you don't have a riven, I will give you two lists of mods to use in the flex slot. A high-priority list and a low-priority list. Higher priority meaning it's a better idea because you will get more value. Please be aware that some of these flex mods will be high drain so you might need to use additional forma.

High priority flex mods:
(Primed) Bane of ___ - for faction damage
vigilante armaments - for more multishot
hammer shot - for more crit damage and status chance

Low priority flex mods:
critical delay - for more crit chance
(Primed) shred or metal auger - for punch through to help with crowds
bladed rounds - for more crit damage
serration - for a bit of extra weapon damage.

In terms of arcanes, it's not complicated. Deadhead or merciless, whichever your preference is. Seeing as this build uses galv scope, it makes more sense to go for deadhead, but both arcanes do the same thing.

The exilus slot. There are three mods that you can choose to take here. You can opt for [Stabilizer], to make getting headshots even easier than it already is. You can take [Hush] for use on invisible frames. And you can take [Ammo Drum] if neither of the other mods suit your fancy. This is what I go with 75% of the time.

Now we move on to companion synergies. The companion specifically is not what's important. It's the weapon. You want a sentinel companion so that you can take the vigilante mod set on the sentinel rifles. Example: [Deth Machine Rifle Prime] with [Vigilante Armaments], fervor, supplies and offence for a 20% chance for your shot to have its crit tiered up. What this means is that there is a 20% chance for your non crits to be yellow, your yellow crits to be orange, and your oranges to be red.

Other companions include smeeta / adarza for crit chance up + armour strip, and panzer for viral and armour strip.

At the end of the guide we come to ability synergies. These are the best abilities to increase the effectiveness of your [Kuva Karak]:

[Xata]'s whisper: Extra status for galv apt, solid damage bonus, can help with headshots.
Nourish : Viral damage & status. enough said.
Roar : Brilliant universal damage boost
Seeking shuriken / Tharros strike / Terrify / Pillage / Psyhic bolts : armour strip is still always useful
Shooting gallery : decent and reliable damage boost. (Do not use [Serration] with this power, it's a waste of a mod slot.)
Eclipse : I generally advise against this ability in general, because of how inconsistent it is, but it's an option nonetheless.

For optimal effect, a critical chance riven is highly desired, and considering this is the [Karak] we're talking about, they won't sell for high prices, so I heavily recommend one. The one I use the most is +Crit Damage, +Crit Chance, +Status Chance, - Free Negative. I actually can't remember right now because I have been trying out a lot of new weapons recently so I forgot, but It's a totally free negative, so more or less a god roll for the [Karak]. As of writing this, unrolled [Karak] rivens are selling for 18+ plat on WFMarket. Once you have a riven, you would slot it over Thermite Rounds.

That's all for this build. I have a viral hunter munitions build: https://overframe.gg/build/522553/ so that's why I haven't used HM in this. But thank you for taking the time to look at my build and reading this short novel of a guide.