melee focus knife + big gun for bosses
 Ogryn Build - Warhammer 40k: Darktide 

Melee focused knife build.
You can use special attack followed by 3 light atks in any circumstance.
But against single target 1 special > 2 light stabs, is better.
And against thick hordes, use Heavy 2 > Light 3, the infinite cleaving combo, also applies way more bleed stacks.

Some notable picks:
Trample gives +50% increase to ANY damage source!
Bombs Away! safest pick so you can revive downed players any time.
Delight in Destruction reduces ANY damage, just like Pumped Up.
No Hurting Friends! is a Power multiplier, with added Toughness Damage Reduction.
Hard Knocks is a Damage multiplier, just like Soften Them Up. 
We also get No Pushover on the way, which is a nice safety net since you generally don't need to push so it should be ready when you need to get out of a corner.

The ranged weapon makes up for our otherwise low boss damage.
Achlys Mk VII Twin-Linked Heavy Stubber is fast to pull up and still accurate in short bursts, enough to kill snipers at any range, delete lines of gunners, and it does the best Monster DPS, even on a melee build with no ranged investment. It's actually faster to reload than the smaller stubbers and its magazine lasts way longer too. Only downside is no Can Opener, (but I have not found many Crushers that would survive the knife after getting punched for more than 3s anyway.) and if you want best boss dmg you can't use Inspiring Barrage either. But we have Steady Grip which works even without shooting, while braced.