[Trumna]: The hot knife through butter. Easily melts away any enemy from steel path enemies, to bosses, and even acolytes. The viral seems to just eat away at health and will kill level 100+ steel path enemies in just 2-4 shots easily. The multiplier from Deadhead causes crazy damage spikes and will melt away any enemies you might encounter. The gun performs even before you proc the mods and arcanes as well. AOE blast will apply viral to surrounding enemies, priming them to be cut down.

I went ahead and bought a riven but can be easily replaced with a mod like [Galvanized Aptitude] or [Internal Bleeding] if you have a riven that has toxin on it. I plan on rolling the riven for toxin instead of the damage to grineer, and then using [Internal Bleeding] for those juicy bleed procs that will work well with the viral. Since the [Trumna] only does heat and impact on a direct hit, it would work very well with [Internal Bleeding] (and I use a similar build on my kitgun and it works charms).

Lastly, if you decide to use one more forma for an exilus, throw [Stabilizer] on there or something.