Best Harlowe Build in Borderlands 4 (Chroma Accelerator)

Harlowe has quickly become one of the most powerful and fun Vault Hunters in Borderlands 4, and her Chroma Accelerator action skill is proof of that. With an endgame build, players are going to ensure every enemy within Harlowe’s line of sight (and beyond) is annihilated in a nuclear explosion, and any of them that manage to survive will be quickly wiped out with rapid fire. Players can find the best Chroma Accelerator Harlowe build in Borderlands 4 right here, and this Harlowe One-Shot build will make it so that you can kill bosses in UHV5 within seconds, and sometimes, even quicker.

This build does NOT need a Throwing Knife with Penetrator Augment to be effective.

Best Skills for Chroma Accelerator Harlowe

Skill	Description	Why It’s Useful
Cyclotron (5/5)	Harlowe gains increased Fire Rate.	More Fire Rate means Harlowe’s going to tear through enemies so much faster.
Neutron Capture (Augment)	All Damage Harlowe’s Unstable Energy Pocket deals to enemies is stored. Whenever it explodes, a portion of that Stored Damage is transferred to Harlowe’s Gun, causing her to deal Bonus Radiation Damage.	Use Action Skill to gain absurdly high damage for 8 seconds.
Fuzzy Math (5/5)	Harlowe gains increased Status Effect Chance.	More Status Effects, more damage!
Field-Ready Prototype (5/5)	Harlowe gains increased Action Skill Damage.	Turn Harlowe’s Action Skill into a nuke with more damage.
Poisoned Sun (5/5)	Harlowe gains increased Radiation Damage and Irradiation Chance.	Really helps the Action Skill to Irradiate and melt enemies.
Chain Reactor (3/3)	Harlowe deals Bonus Radiation Damage to Entangled enemies.	Radiation Damage is already buffed, and Entangled enemies are those affected by her Action Skill.
Fissile Launcher (2/3)	Whenever Harlowe damages an Irradiated enemy or an Entangled enemy, shoot a Radiation Dart at another enemy.	Helps with ad-control.
Demon Core (Capstone)	As Harlowe’s Unstable Energy Pocket travels, it shoots Radiation Darts at enemies. Whenever Harlowe Entangles an enemy while her Action Skill is active, automatically Irradiate that enemy.	The real kicker from this is to irradiate enemies with the Action Skill to make them weaker.
Mechanical Brilliance (5/5)	Whenever Harlowe damages an enemy with a Skill, she gains increased Skill Damage. This effect stacks.	Use Action Skill, deal more damage. Simple!
Practical Applications (5/5)	Harlowe gains increased Skill Damage.	Further increase the nuclear power of Harlowe’s Action Skill.
Make Extraordinary (5/5)	Harlowe gains Critical Hit Chance with all Skills. This chance increases every time Harlowe Entangles an enemy. This effect stacks.	Use your Action Skill to see an absurdly high Critical Hit Chance for 8 seconds.
Periodic Table Flip (4/5)	Harlowe gains increased Elemental Damage, Status Effect Application Chance, and Cryo Effectiveness.	More Elemental Damage and Status Effect Chance helps to irradiate.
Bright Future (4/5)	Whenever Harlowe triggers or retriggers an Action Skill, she gains increased Fire Rate.	Even more Fire Rate upon Action Skill use.
Ripple Effect (1/1)	Kill Skill. Whenever Harlowe kills an Entangled enemy, automatically Entangle another nearby enemy.	A chain reaction of squishy enemies getting killed.

This build is very simple to use, and here’s what you need to do when facing a boss:

Use the War Paint Repkit
Pop your Action Skill
Fire your Vladof Assault Rifle

That’s the basics, and that’s what makes this build so good. With these aspects, players are going to see Harlowe’s Action Skill fire at enemies and detonate, which then absolutely annihilates the boss, making them extremely weak to damage and increasing your Fire Rate. As soon as you’ve used your Action Skill, your rapid-fire Vladof Assault Rifle will wipe them out, and you don’t even need a Penetrator Augment Knife for this. However, if you do have one, use it before the War Paint Repkit.

Best Weapons and Gear for Chroma Accelerator Harlowe

Only 2 things really matter for this build, as everything else can be used by what you feel the most comfortable with. However, we’ll list everything we use and where you can farm them so that you can fully optimize the build.

Firstly, there are the weapons. We used either of these Assault Rifles: Lucian’s Flank (Meathead Riders, Old Scrape Ripper Drill Site, Cuspid Climb, Terminus Range) OR Aegon’s Dream (Horace, Horace’s Oversight, Hungering Plain, Fadefields). Really, the main reason to use these Assault Rifles is because they’re Vladof with the Extra Barrel Alt-Fire, which comes with an absurdly high fire rate. Both are good options, as Lucian’s Flank returns ammo on Critical Hits and Aegon’s Dream provides Incendiary and Cryo damage. A high Rate of Fire Assault Rifle is essential for melting bosses.

To further increase Fire Rate, you’ll want to use the Shiny War Paint Repkit (Meathead Riders, Old Scrape Ripper Drill Site, Cuspid Climb, Terminus Range). This Repkit has decent healing, but the main use from this comes from how it increases Fire Rate and Movement Speed. Another aspect of increasing Fire Rate and Damage comes from Enhancements. Players are going to want to use any Enhancement that focuses on Vladof-licensed parts, like Box Magazine to increase Fire Rate and Magazine Size, or Bullet Hose to provide a Chance to add an extra Projectile per shot.

For the Class Mod, use anything that increases Skill Damage, but we went for the Skeptic Class Mod (Callis, the Ripper Queen, Moon-Called Throne, Fallen Crown, Carcadia Burn), not for the skill bonuses, but for the fact that shootign enemies with an active Status Effect restores Action Skill, making it so you just have to shoot enemies to get your abilities back.

The Shield doesn’t really matter, but we went with Firewerks (Splashzone, Riptide Grotto, Coastal Bonescape, Fadefields) because being able to see automatic Missiles shoot enemies when killed just really helps ad-control, but anything works. Lastly, Ordnance really does not matter as you won’t be using it, but if you want to make this build go off the rails, use a Throwing Knife with Damage Amp Payload and Penetrator Augment for Critical Hits and to increase Damage Taken against the enemy, but again, this really is just overkill, and you don’t have to use it.

Best Specializations for Chroma Accelerator Harlowe

Specialization Perk	Description
Now With Caffeine	Reduce Action Skill Cooldown whenever a Repkit is activated. Action Skill Cooldown Reduction: 25%
I Am A Gun	Action Skill Damage now benefits from increases to Gun Damage. Action Skill Damage: 50% of increases to Gun Damage
A Honed Mind	Action Skills gain a chance to Critically Hit enemies, and also gain increased Action Skill Critical Hit Damage. Action Skill Critical Hit Chance: 5% Action Skill Critical Hit Damage: +50%
Riddle You This	Whenever the Vault Hunter deals Gun Damage, gain a Stack of Riddle You This, increasing Gun Damage. Stacks are lost if a new Stack has not been gained for 6 seconds. Gun Damage: +1% per Stack Maximum Stacks: 50

For Harlowe’s Specializations, you’re going to want to focus on 10 Points in Sharpshooter and 10 Points in Runner, specifically so that you can unlock Daredevil. With Daredevil unlocked, bump it to 20 for the increased Action Skill Cooldown Rate and all 3 skills within this tree. If you have any left over points, place 20 into Brute and at least 20 more in Survivor, then use your remaining Points to continue investing into Daredevil.

Best Firmware for Chroma Accelerator Harlowe

Firmware	Bonuses	Slots
Bullets To Spare	Gun Fire Rate is increased by +5% Gun Magazine Size is increased by +20% Gun Fire Rate is increased by 50% of Gun Magazine Size	3
GOOFJC	Action Skill Cooldown Rate is increased by +10% Action Skill Damage is increased by +15%	2

Firmware

Bonuses

Slots

Bullets To Spare

Gun Fire Rate is increased by +5%

Gun Magazine Size is increased by +20%

Gun Fire Rate is increased by 50% of Gun Magazine Size

GOOFJC

Action Skill Cooldown Rate is increased by +10%

Action Skill Damage is increased by +15%

Harlowe’s build is extremely dependent on her Fire Rate and her Action Skill. As such, we decided to use 3 pieces of equipment with Bullets To Spare so that we can increase the Fire Rate by +55%, along with a +20% increase to Gun Magazine Size. This build is so optimal, you won’t even need these extra stats, but they’re there for overkill. Bring along 2 pieces of gear with GOOFJC so you can increase your Action Skill Cooldown Rate by +10%, and your Action Skill Damage by +15% to really pump out an unstoppable nuke.