[Tenet Cycron] is one of my most used secondaries because as previously mentioned it's very comfortable to use. It is a battery weapon and Cacadia Flare means it isn't as reliant on kills to do damage in a pinch. Best paired with weapons that need to run ammo mutation mods as a "[Plan B]".
Flex slot is [Creeping Bullseye] which can be replaced for [Primed Pistol Gambit] (which is technically more DPS but runs out of magazine faster so this is more of a "for freel" mod) and the optimal [Galvanized Crosshairs].