Havoc 40 shivs hive scum (no needle pistol)
 Hive Scum Build - Warhammer 40k: Darktide 

This is by far the best solo hive scum build Ive played with. 

Switch out tertiums welcome for jittery, i often do and doesn't affect my dps to much.

I also often swap quick and deadly for splash damage, the dps at the end of game is about the same, youll be worse into bosses but youll clear mixed hordes 3-5 seconds faster, or kill a whole pack of ragers by killing three in a row over time, and bring down everything around it to one taps. 

If you are into the havoc modifiers orange and red, I highly recommend dropping carapace on the shivs for maniac and dropping jittery, quick and deadly, or maxed out chems for hypercritcal, putting your stimm the same but triple attack speed and triple cooldown. enemies with the last toll modifier need to be one tapped idealy, and we do not care about "breaking" our hyperviolence train as long as the invincible unstaggerable ragers die.

If into a auric modifier thats scab only, where you KNOW there will be rows of crushers, the rending node on ult will often bring crusher to one or two shots instead of two to three. I also recommend this node if you drop +carapace on the shivs if you are struggling with rager packs, esspeciallly when the servers are lagging. 

Take the needle pistol when needed, look at your team comp. If your team has no boss dps besides you, then bring it. Otherwise the dual pistols, bolt pistol or shredder autopistol will serve you much better as a sidearm. The dual pistols have the best dps/breakpoints to ammo spent, and are consistent, but don't stagger as well as the other two options. Do not bring the Infantry auto gun, dual autopistols, or braved autoguns. Those need dedicated builds to be functional, esspecialy into havoc. 

This build functions very well with the tac axe with shred and power on hit blessings, but swap the stim off weakpoint damage and over to crit. DO NOT take the tac axe into red and orange modifiers together. The weapons main advantage of stagger and attack speed will be countered. Tac axe does often struggle into armor more so needle pistol can help here, but I dont find it neccesary as long as you keep your ult up.