GrimTools: Warlord, Level 100 (GD 1.2.0.3) - Grim Dawn Build Calculator
Image by DALL-E
Two short strikes to bait your opponent into exposing an opening, followed by with a disarming shriek and a powerful follow-up blow. As your opponent reels from the attack, follow through with a clean sweep to succinctly end the fight.
This is the highest single-hit damage that I’ve achieved in a build so far, at 3.76m damage. But let it be known - This is not a very good build. 
Update
On May 5 2024, version [1.2.0.5], I hit 4.45M damage.
Edit: Image of 4.45m critical hit
Edit: Video that the screenshots are from - skip to 3:20 to see the 4,456,651 damage crit. And lol at how mediocre the build is in general despite it’s massive spike damage
Original Post
This build is built around crit damage. The build has 159% crit damage with all buffs firing, and Blade Arc gets an additional 105% crit damage (35% from weapon, 45% from Laceration, 25% from Clean Sweep), bringing it to 264% crit damage on Blade Arc. On top of that, Clean Sweep gives it a +175% total damage bonus to it, allowing these crits to go through the roof.
Despite the build’s potential for massive spike damage, it’s actually kind of an average build. It’s squishy. It takes spike damage. It’s got poor CC resists, low phys res, low healing and limited damage absorption. It has very limited resistance overcaps. Even in terms of it’s damage output - It regularly hits decently due to Cadence, Blade arc and it’s overall crit damage, but it’s OA is low for a crit build, and it’s inconsistent. On top of that, the build is so heavily reliant on a range of temp buffs to keep it’s damage high, and it’s damage is meant to be the one thing going for it. So, the one thing going for this build is inconsistent making the build ‘inconsistently good’.
Temp damage buffs include:
- Fervor
- Might of the Dire Wolf
- Battlecry
- Fighting Spirit
- War Cry (long cooldown = 2.5 seconds when enemies aren’t affected by the RR)
- Ascension
- Ulzaad’s Decree
So to land a super crit requires that all of these are active, all debuffs are active on an enemy, and you roll well for damage RNG, and you happen to crit an enemy who probably already has low physical resists. It’s a bit niche. But, it’s not impossible to achieve 
I didn’t get the 3.76m hit on video, but I did get this 3.75m hit on video. Skip to 1:25:
Crucible 100-110 with Cruci Buffs
It’s worth noting that the 3.76m damage was achieved with crucible buffs, but without the use of Sanctified Bone or Prismatic Diamond total damage buffs (or damage vs undead / chthonics). Combined, that’d be another 18% total damage vs an enemy, so the potential damage for this kind of build with some tweaks could be loosely calculated at something like 3.76m * 1.18 = 4,436,800 damage. 4.4m. Hot damn. So I might have to try that in a bit. So I might have to try that tomorrow, but for now I was very, very happy with this sort of single hit.
Enjoy~