Borderlands 4: Harlowe Radiation leveling guide

Nuking bosses in Borderlands 4 with weapons is fun, but with Harlowe’s CHROMA Accelerator, you can fire an actual nuke. It can be used as a mob-clearing ability or can be detonated on command to deal a large amount of damage to bosses. With the proper setup, you’ll also be able to buff your weapons to deal additional damage.

This guide will take you through the entire leveling build you can use throughout the campaign and early endgame.

Pros and Cons of this Harlow Radiation build in Borderlands 4

Harlowe’s CHROMA Accelerator deals impressive damage (Image via 2K)

Before you start your Harlow Radiation build, it’s essential to know its strengths and weaknesses.

Strength

Damage: With Harlowe’s Radiation build, you don’t have to worry about damage. Once you activate the Action Skill, any enemy within its range will die. If not, the build will boost your gun damage to take down any stragglers.
Easy to play: Not only is the build fun, but it is also easy to play. All you need to do is shoot your Action Skill and use your weapon to chain radiation bolts across enemies.

Weakness

Action Skill cooldown: The only thing that may hold the build back is the cooldown for CHROMA Accelerator. You'll need to invest in as much cooldown reduction as possible for maximum DPS.
Gear-dependency: While you aren’t using your nuke, you’ll be using weapons that need to synergise with the build to deal damage. Meaning you’ll need specific gear to maximise the damage.

Borderlands 4 Harlowe Radiation campaign build: Level 1-30 skill order

Initial investment up to level 30 (Image via 2K)

Leveling up can be tedious, but it is essential to achieve the build you want. If you’ve completed the campaign in Borderlands 4 and unlocked Ultimate Vault Hunter difficulty, you’ll have access to Level 30 Harlowe.

Regardless of how you start, following the upgrade order for the passives will provide a smooth leveling experience:

Cyclotron (5/5)
Neutron Capture (Augment)
Elementary (5/5)
Enriched (3/3)
Test Subjects (2/5)
Poisoned Sun (5/5)
Chain Reactor (3/3)
Fissile Launcher (2/3)
Dirty Bomb (1/1)
Demon Core (Capstone)

Note that you’ll need to sacrifice a few points across the board to unlock the Demon Core. Acquiring the Capstone as soon as possible will help in better mobbing, which in turn results in faster level-up. Once you have Demon Core, put three more points into Test Subjects and the remaining point into Practical Applications.

Gearing for Harlow Radiation leveling build

Plasma Coil is an incredible Legendary for Harlowe's Radiation build (Image via 2K)

As the build name mentions, you’ll be focusing on radiation damage. That means the weapon and ordinance you use should also deal the same damage. Finding the perfect weapon with radiation damage may take a lot of time; that’s why you should use any decent SMG or Assault Rifle you can get at the beginning.

Having an automatic weapon to hold down the trigger should be a priority. If you have completed the campaign, get the Plasma Coil SMG by defeating the Timekeeper. The gun drops with Radiation and a random elemental damage.

Plasma Coil is a Maliwan weapon, so having the enhancement with the ‘Maliwan Synthesizer’ perk will further boost damage. Additional perks can include increased magazine size, gun damage, or fire rate.

There’s no need for a Legendary Repikt, but having Elemental Affinity or the Accelerator perk will help increase damage. Accelerator is the ideal perk as it grants 100% Action skill cooldown for the next eight seconds. Here’s a list of everything you’ll need to equip.

Gear	Suggestions
Weapon	Radiation-based with a high fire rate or Plasma Coil
Repkit	Any Repkit with the Accelerator perk
Ordanance	Radiation-based high-damage ordnance
Enhancement	Anything with SMG damage, fire rate, or status damage
Class mod	SMG damage, Action Skill damage

Borderlands 4 Harlow Radiation build: 30-50 Skill order, and endgame pivot options

After level 30, most of the points will go into the green tree (Image via 2K)

After crossing Level 30, it’s time to branch out towards another tree. To further increase the weapon and skill damage, we’ll be using skills from the Cosmic Brilliance (green) passive tree. Here’s the upgrade route:

Momentum (5/5)
Neutron Decay (5/5)
Resonance Cascade (3/3)
Confirmative Reality (3/3)

After investing 16 points into the tree, you’ll have four remaining. Invest them in Practical Applications within the main tree for more skill damage.

Endgame pivot options

The Specialization tree opens up a lot more build possibilities (Image via 2K)

After completing the campaign and unlocking the specialization window, you can play around with the passive to tweak the build or move on to a different one. For example, instead of Cosmic Brilliance, you can invest in Zero-point to further lean into a crit-based build.

As for the specialization tree, perks like Now With Caffeine will further improve Action Skill cooldown, while Honed Mind will improve critical hit chance and damage. For weapon-based gameplay, perks like I am A Gun, Bullet Train, and The Best Defense are the best options.

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About the author

Mayank Singh Rathour is an MMO writer at Sportskeeda. He graduated from college with a degree in Business Administration and has over two years of experience as an esports journalist.

Mayank was introduced to gaming at an early age and played Contra, Double Dragon, Castlevania, etc., on his Nintendo DS. When he was a little older, Counter-Strike — a title that majorly helped develop his passion for gaming — became his favorite pastime. Though he's played a bunch of games since then, his love of CS has remained strong. Shroud, a former Counter-Strike: Global Offensive pro, is an inspiration to him. He's also a fan of series' esports scene, following teams like Vitality, NAVI, and The Mongols closely.

When Mayank has some free time, he plays basketball and helps people build PCs.

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Edited by Mayank Singh Rathour