Haja-no Ontachi, or the Great Evil-Cutting Blade

I've been using this weapon since Tenet weapons first dropped and it's never failed me once. It should be noted that I am using this weapon alongside an [Excalibur Umbra] that is built for survival and tankiness, with a ranged weapon that primes enemies with Viral for additional damage whilst closing the distance.

This [Tenet Livia] has innate Electricity damage, so plan your elements accordingly.

Thanks to the wonder that is the Granum Attache, this weapon retains its combo whenever you put it away in favor of another weapon. Practicing the art of quickly smacking your right-click to whip out your pistol means you can retain a 12x combo multiplier for an entire mission once you [Reach] it. That's a total of 300%+ critical chance modifier. Even with no mods on to increase your critical damage, that's a beautifully nasty damage multiplier that has this weapon keeping up during Arbitrations, Steel Path Effervo runs, and Netracells.

Everything else is all about getting high damage and keeping your health up. Thanks to [Discipline's Merit], Tennokai opportunities come every 4 hits, which means that every 4 hits you have a free chance to fill your health back up to full. Tested on an [Excalibur Umbra] with roughly 1800 HP, when reduced to below 100 HP this brought his HP back up to full every time. Even with Life Strike taking up a slot, this build hits 20m Red Crits semi-consistently.

Your eyes are not deceiving you, [Life Strike] is sitting in the wrong polarity slot. This is because that slot is meant for a Madurai polarity, and Life Strike is simply the filler for missions where you need more sustain/health recovery, or Narmer missions where faction mods don't count. This slot can be filled with any Smite Faction mod you happen to have, making the build versatile enough to fit most content.

Go forth, and smite evil.