This is a Quassus build for endgame/level cap for Grineer mostly since the build is made to be run at 12x for [Blood Rush] with a high crit multiplier for better slash procs.
Rocks Grineer Demolysts either they are primed with viral or not. Not a fan of the 2x spam heavy attack builds since you do lose out on a lot of scale.
This weapon is best played as built-up multiplier melee , used with an [Epitaph], [Ignis] or a good viral primer to make the slash procs go OOF.

IDEALLY you want a Riven for this weapon since it helps a LOT.

If you can get a riven with : Heavy att efficiency - Crit dmg/crit chance - Melee Damage then PERFECT.

You want your riven to be able to replace mods to free up space (except crit multiplier and melee dmg). For example if u roll 60+ heavy att efficiency you can replace [Reflex Coil] for more damage.

What you want the most is MELEE DMG+CRIT MULTIPLIER+CRIT CHANCE because slash procs scale with that the best.

VS Corpus and enemies with a lot of health you'd want [Primed Fever Strike] for more raw damage.

I have multiple rivens with heavy att efficiency+melee dmg+ random useful kinda bonus and it helps a lot with keeping up combo while making space for other damaging mods.

It will still [Shred] like this but if u want more and can afford it, slot in Arcane Blade charger and use a viral primary that can apply status and grab kills so you can both prime viral and feed 300% melee damage into your melee !!! If you dont have Blade Charger or want a quality of life mod, then use Arcane Strike OR [Primed Fury] if your riven allows you to replace something on your weapon.

Attack speed makes Heavy attacks on [Quassus] much faster and also allows you to stack the combo up easily. You'll never fall bellow 7x even when spamming heavy attacks because of the 90% efficiency, and trust me 4.9x at 300%+ crit chance will kill anything with huge bleed numbers.