flailing maniac/grenade freak (OUTDATED)
 Veteran Build - Warhammer 40k: Darktide 

Hybrid build for maxing out crits/attack speed with the Mk VII tac axe with some shredder grenades for when the situation calls for it.

The main talents that make this work are the 2 grenade talents Demolition Stockpile and Demolition Team which will provide a guarantee grenade every minute and a chance at a grenade every time any specialist or elite from either you or any allies in coherency to provide a grenade. These 2 talents are great for keeping uptime on grenades and allows you to give the map found grenades to the other classes without self sustain capabilities. (using lethal Prox on the bolt pistol will boost the range of the shredder grenades bleed radius letting you catch more enemies but is not needed)

After that there are 3 talents that make tac axe have some lighting fast swing speeds with some pretty generous crit chances/weak spot damage as well. these are Reciprocity, Desperado, and Trench Fighter Drill. Reciprocity gives you a 5% crit chance whenever you dodge an enemy attack capping out at 25% for 8s and can be refreshed once at max stacks. 

Desperado grants you a flat 10% Crit Chance and 25% finesse bonus for every melee weapon. this paired with the tac axe's crit boost, perk, and Vets base crit chance gives you roughly 57% Crit Chance. (I'm aware that there is a 5% crit chance node above the close kill aura but losing Survivalist and the extra cost of points for taking a longer route weren't worth it). Finally Trench Fighter is self explanatory and grants a free 10% attack speed without any setup required. it's great for boosting damage against beefier enemies or for keeping hordes of pox walkers out of melee attacks,

For the Key stone it's ENTIRELY OPTIONAL on whether you want to take Weapons Specialist for the 15% extra attack speed or if you want to respec the 3 points towards something else on the tree. If you do use the keystone you'll need to keep track of your melee specialist timer and swap to your ranged weapon when the timer runs out to reapply the melee buff. using the Bolt Pistol is the best option personally since it can buff your grenades (as stated earlier) with a small enough mag size to benefit from Always Prepared on top of having high enough base damage to reliably 1 shot most chaff enemies.