Wholesale Slaughter
 Veteran Build - Warhammer 40k: Darktide 

Heavy Sword is for horde and mixed enemy clear. H2 can work as a vanguard attack despite being a Strikedown, thus incredibly useful as a high damage horde clear attack. L1 > H2 therefore is a good combo for crowds. If it's only Groaners or Poxwalkers you can spam light attacks. H1 is a vertical strikedown attacks very useful against those annoying Vanguards as you can hit them in the head above their shields.

Heavy Sword's special attack is its main stagger source against targets like Ragers. There is also a hidden attack for this weapon where if you follow the special attack with a light attack, that light attack will also do high stagger and can cleave through carapace armor. It's probably the only attack that can cleave through carapace without a blessing. Therefore, Special Attack > L1 can be used as an opener against groups of Maulers, Ragers and Vanguards to stagger a bunch of them at once. It can one shot Dreg Ragers and Mutants with weakspot hits as it does significantly high damage to Maniac type enemies.

Infantry Autogun is the wildcard here as it can clear hordes, kill Specialists both nearby and far, and it can kill Crushers, Monstrosities etc. Infiltrate, Focus Target and Deadshot all work in tandem here. Infiltrate gives you 30% damage boost for 8 seconds, Focus Target increases damage by 30% and Deadshot increases crit chance considerably and reduces sway. You can kill a Beast of Nurgle with one magazine just by shooting it in the mouth. Watch your stamina drain though, as Deadshot will drain it, which is why we have two 12% stamina regen perks on our curios.

Shredder grenades also require a special mention here. First of all, feel free to use one grenade every now and then to stagger groups of enemies to create an opening as you will regenerate them quite quickly. But the main benefit comes from the Infiltrate and grenade combination. Whenever you get overwhelmed by high enemy numbers, activate Infiltrate and underhand throw 3 (or all 4) grenades among the crowd. Anything other than Crushers will die either to explosion damage or bleed stacks. Crushers are resilient due to underlying carapace armor but rest will perish easily. I call this the "makeshift Ogryn nade" that you can regenerate! Pay attention to underhand throwing as it doesn't break invisibility. But if you throw them normally, it will break invisibility. I don't know if this is a bug or if intended, but it is what it is.

Lastly, you can swap Desperado with Agile Engagement but I find it hard to effectively utilize Agile Engagement. But if you are capable, it's definitely a choice.

Enjoy!