Certainly the best Barbarian build & of the best endgame builds overall. Hammer of the Ancients with Grandpapa is a truly insane combination in Diablo 4.

Gear

• Weapon: The Grandfather

• Mace: Penitent Hammer of Limitless Rage/Bloodsucker of Ancestral Force/Edgemaster's Crag Hammer

• Legendary Ring: Bold Chieftain's Circle

• Boots: Ghostwalker Boneweave Treads

• Pants: Tibault's Will

• Legendary Ring: Loop of Echoing Fury

• Helm: Harlequin Crest

• Chest Armor: Primal Breastplate of Disobedience

• Gloves: Relentless Berserker's Warlord Gauntlets

• Legendary Aspect: Ghostwalker Mobility Aspect

This 50 Tibault's Will that we're getting is multiplied by all of our Fury generations, and it's multiplied if we have rant cry active as well, it just up instantly it gives us like 200 plus fury because it also gets us Unstoppable, and what you can do is like if you notice the cool down here you can reduce it by attacking or you can reduce it by casting one of your shots then if you press it when you're not Unstoppable boom you get the full resources again and you like can do this like all the time basically if you do it if you time it, you can smash, you can do all kinds of things and you get your resources back.

Vampiric Powers

We have Blood Boil for guaranteed overpower, we have Prey on the Weak, together with Metamorphosis, the curse makes everything vulnerable this is how we blast the boss this is also how we activate our two hand expertise how we activate the vulnerable multipliers things like that then we have fortify with Sanguine Brace, we just kill on hit and we have some fortify generation of Pon board just per fortify easily, then we have Undying here, this one gives us a lot of damage reduce when we have lower health and when we're fortify as well it's just going to all kick in together.

Skill Tree

• Basic Skill: Lunging Strike, Enhanced Lunging Strike

• Core Skills: Hammer of the Ancients, Furious Hammer of Ancients

• Defensive Skills: Imposing Presence, Rallying Cry, Enhanced Rallying Cry, Iron Skin, Tactical Iron Skin

• Brawling Skill: War Cry, Raid Leader, Aggressive Resistance, Prolific Fury 

• Passive Skill: Pit Fighter, Thick Skin, Counteroffensive

• Ultimate Skills: Heavy Handed, Wallop, Brute Force, Wrath of the Berserker