*Borderlands 4* has exploded with powerful builds since launch. Whether you’re aiming for solo runs, co-op destruction, or end-game dominance, there are builds that break the meta. This guide covers the **best Vault Hunters**, the tricks behind *infinite damage builds*, and how to choose skill trees, gear, and augments to dominate bosses, mobs, or both.

1. Infinite Damage Build (Boss-Melter Style)

One of the hottest builds recently discovered is the **infinite damage build**. If you can get your hands on the *Vampiric Vivisecting Throwing Knife* with the *Penetrator Augment - Damage* stat, paired with the right Vex passive skills (**Bloodletter**, **Contamination**), you can melt bosses in under **10 seconds**.

How it works:

• The knife causes your regular damage to count as critical hits via Penetrator.
• Vex’s *Bloodletter* adds bleed damage over time, which gets multiplied by criticals.
• *Contamination* boosts status-effect chance, making the bleed proliferate.
• Stacked together, each tick of damage feeds new status effects, triggering more damage in a cascading loop.

This build is **incredibly powerful** for endgame bosses—but keep in mind, it’s likely to get patched. Make sure your gear and augments support bleed, status effects, and high critical damage. Also, focus on survivability so you last long enough to see the loop work.

2. Best Builds for Key Vault Hunters

Each Vault Hunter in *Borderlands 4* has multiple skill trees, capstones, and unique action skills. Here are some of the best builds for popular Hunters: Vex, Rafa, Harlowe, Amon. Mobalytics, PC Gamer, and other guides are central sources for these.

• Vex (Siren): The **Summoner** build using *The Fourth Seal* tree, where she summons Reapers and Specters for damage and tanking, or the **Witchy Trigger Finger** build focused on crits, kinetic damage, and kill skills.
• Rafa (Exo-Soldier): Builds like **Critochet** (focused on ricochet & critical hits using Peacebreaker Cannons), **Arcstrider** (melee crowd control / sustained damage with Arc-Knives), and **Gunzerker** style (dual-wield firepower and fast reloads) are strong. :contentReference[oaicite:5]{index=5}
• Harlowe (Gravitar): Builds like *Dirty Bomb* (radiation / elemental AoE), *Ties That Bind V2* (crowd control + freezing status), or *Nuclear Winter* (overshield synergy + elemental damage) are great for either mob-clearing or team fights. :contentReference[oaicite:6]{index=6}
• Amon (Forgeknight): For melee / elemental combos, **Iceplosions build** and **Cyber Viking build** mix action skills, elemental effects, and strong cooldown reduction.

3. Solo Vs Co-Op / Endgame Considerations

If you play solo, you need builds with self-sustain, crowd control, and survivability. The Summoner Vex build and Rafa Arcstrider are strong solo choices. For co-op or endgame boss raids, burst damage and status-effect heavy builds like the infinite damage Vex setup or Harlowe Radiation builds shine. Look for builds with good augment synergy, capstones that increase Action Skill uptime, and gear that boosts your critical / status damage.

4. Gear, Augments & Capstones – What to Prioritize

To make any of the above builds work smoothly, you’ll need the right gear, augments, and capstone choices:

• Gear with **high critical damage**, **status effect boosts**, and **fast weapon-reload or fire rate** where applicable.
• Action Skill augments that reduce cooldown or expand uptime—especially those that let you re-cast quickly or boost damage over time.
• Capstones that significantly increase your core build direction: whether that’s bleed stacking, minion strength, or damage multipliers. Don’t spread too thin. Focus into one capstone relevant to your playstyle.
• Weapon choice matched to build: e.g., throwing knives for bleed or critical builds, cannons or shotguns for burst, elemental weapons to trigger status effects.

5. Sample Build: Harlowe One-Shot / Burst Combo

Here’s a tested sample build that many players are using for high burst damage and team utility:

**Harlowe – One-Shot / Burst Build** (with team utility support): radiation focus, early points into *Neutron Decay* (5/5), double-casting *Group Study*, using *Confirmative Reality* to reduce Action Skill cooldown, and stacking in *Mass Function* for reload speed. Use a radiation grenade to open fights, dump crits, then reset. This works surprisingly well in both solo boss fights and co-op engagements.

Conclusion

Borderlands 4 offers a rich system of builds that cater to a wide variety of playstyles: solo players, co-op teams, burst-damage lovers, and status/effect masters. Whether you chase an “infinite damage” exploit or prefer a balanced build that survives long fights, the key is skill tree focus, good gear, powerful augments, and adapting build for your preferred Hunter. Experiment, optimize your build, and dominate those Vaults.