Havoc 40 EASY Arbites
 Arbites Build - Warhammer 40k: Darktide 

I've done multiple Havoc 40's with this.

This has to be the easiest build to run.

 

Single Target: Push > Push Attack (uppercut) + Light Attack (diagonal strikedown)

This is such an OP move for no reason and it is a quick attack to get out. I literally spam this. Between the stamina regen on the Curios and the talent RAPID MOVEMENT, your stamina is basically unlimited and not needed to be managed even though your constantly pushing. Can even be used for horde clearing.

Horde Clear: Push > Push Attack (uppercut) + Heavy Attack (horizontal swipe)

Deals great damage and staggers basically everything in front of you. Little better for horde clear. And by hitting 3 enemies with it you trigger SUPPRESSION PROTOCOLS giving you DAMAGE REDUCTION. So you're just a straight up tank swinging beast.

Overwhelmed by horde and Elites: Activate Special Attack + Light Swing (horizontal) SPAM REPEAT

You can activate and swing this, then repeat spam this so quickly its unreal. Just spam this if you're ever stuck in a corner and walk forwards... watch how you push through a crowd easily. Activate, swing, Activate, swing, Activate, swing, quick as you can. The only time you will have an issue with this NOT working is if you have the Havoc mutator "Final toll" active where they turn red and become immune to crowd control. Even then it can sometimes be bypassed or just straight up kill the enemy (because Final toll activate when theyre half health so theyre weak anyway). Use this when you're in a pinch.

Bosses: Target your dog onto it, blow up your dog to stagger the boss, pull out your bolter and activate Castigators Stance and just dump the clip into its Face/Weakspot.... CONGRATS you've just melted 75% of the bosses health bar. 100% if its a weakened version.

Build:

The dog constantly running around targeting ranged enemies keeps you safe to smash through hordes. Every time your dog kills something, which is all the time, you get DAMAGE REDUCTION. I have my Crusher out 80%of the time, only pulling out my Bolter for Bosses, Crushers, Packs of Armoured enemies (Scab Ragers, Scab Maulers etc). The dog keeps damage reduction up constantly aswell as your crusher hitting 3 enemies with each swing. Use Castigators Stance anytime you take heavy damage, i use it constantly, the uptime is really good because again, the dog is going around killing marked enemies which boosts your Ability Regen. Use your dog explosion when you're stuck in a pinch, spam your weapon special, once you get the hang of things and when and where to use them, you'll be almost unkillable.

Carapace on the Crusher because we will get a lot of headshot hits, which are mostly Carapace helmets on important enemies. We do plenty damage to flak enemies without a boost. Then Maniac damage to help with almost everything else that doesnt have armour. Mutants, Ragers, Trappers, etc. Everything on the weapons is to maximise damage. Play this exactly as it is, and you'll be fine. 
NOTE: 30 Stacks of KEEPING PROTOCOL is crucial for boss killing when paired with MONSTROSITY HUNTER.

Its just so easy to use you have to try it.