Updated. This not only kills even faster than before, but now that it's Corrosive + Heat instead of Viral + Heat, we can get synergize with Nourish or a primer companion to still get those viral procs. This shaved about 2 seconds off killing a lvl200 SP Nox from the previous rendition. (From about 7sec to slightly under 5 sec now without using any synergies)
I'm also linking another option which is pretty equal to this one in TTK, but has a higher KPS due to higher fire rate. It's also pure Heat and lower investment.
If you prefer to stay in Peacekeeper mode longer use this build, if you prefer in and out of Peacekeeper mode or against weaker enemies use this alternative build:
https://overframe.gg/build/331371/regulators-prime/equal-ttk-higher-kps-faster-aim-ring-depletion-alternative/
Who doesn't love options after all?
All testing is done with my [Mesa] build without any other synergies, buffs, pets, or whatever.