A Vex build in Borderlands 4 is shredding bosses in seconds. It hinges on one throwing knife stat and two passives that loop status effects into critical hits. The method surfaced via YouTuber NickTew and is already making the rounds. Expect a fix, but for now it works — and it’s simple to set up.
What the build needs
You only need a specific throwing knife roll and two Vex passives to start the chain. The item’s level barely matters.
- Weapon: Vampiric Vivisecting Throwing Knife with “Penetrator Augment – Damage”
- Core passives: Bloodletter (applies bleed DoT) and Contamination (pushes status application chance up to 100% via crits)
- Source: NickTew’s video guide
Once equipped, the knife converts your normal damage to critical damage, so the bleed ticks from Bloodletter count as crits. Contamination then raises status application to 100%, so each tick applies another bleed — a feedback loop that ramps damage to absurd levels. In short: throw the knife, tag the boss, and watch its health disappear.
Why it melts bosses
The build forces every damage tick to become a critical bleed, which then guarantees more bleeds. That’s why health bars drain in a few seconds.
- Critical conversion turns small hits into big ones
- 100% status chance means every tick spawns more ticks
- The loop ignores boss health pools; survival becomes the only limiter
- Knife level doesn’t matter if the stat is present (a level 35 knife worked on a level 50 character in testing)
The important bit is how Contamination compounds the effect. With crit-based status at 100%, the bleed keeps refreshing itself. That’s why players are seeing sub-10-second boss kills on fresh characters. It’s not fancy min-maxing — it’s mechanics stacking too cleanly.
Where to farm the knife
Drops can be rare, but players point to a reliable area. If you need a route, there’s a clear video guide.
- Farm location: Splashzone (southern part of the map)
- Community tip: Reddit threads highlight Splashzone as a hotspot
- Route guide: Ki11erSix’s walkthrough is handy if you’ve not unlocked the area
Once the knife drops, you’re set. Because the crucial stat behaves the same across levels, you don’t need to chase a max-level version before it works. That lowers the grind — and explains why footage of the build spread so fast after launch.
What to spec and what to avoid
There’s not much to it, but a few points help. Some co-op quirks also apply.
- Spend points into In The Zone for comfort and uptime
- Prioritise survivability so you can stand there and let the loop tick
- Co-op caveat: reports say the knife doesn’t stack properly if more than one player uses it in the same fight
- Expect nerfs — Gearbox is planning more endgame bosses and probably doesn’t want one-tap melts forever
If you plan to farm seasonal bosses or endgame rotations, this is the week to try it. Odds are high a balance pass will cap the loop or change how crits interact with status effects. Diablo 4 had its own “infinite damage” episode — and that didn’t last either.
What exact item do I need for the Vex build?
A Vampiric Vivisecting Throwing Knife with the “Penetrator Augment – Damage” stat. Any level works as long as the stat is present.
Which skills make the loop go “infinite”?
Bloodletter applies a bleed that counts as critical damage thanks to the knife. Contamination then raises status application to 100%, so every bleed tick starts another bleed.
Is this safe to use in co-op?
It works, but reports say the knife effect breaks if more than one player runs it in the same fight, so coordinate builds. Expect a nerf soon.
