Tbh FL4K is the crit machine of Borderlands 4 and if you're not building around Fade Away and infinite critical hits you're basically playing him wrong, like the entire character is designed around this fantasy of cloaking repositioning and then unloading a magazine of guaranteed crits into some poor enemy's face and then doing it again 3 seconds later because your action skill cooldown is already back up, I mean the first time you pull off a perfect Fade Away rotation and watch a boss's health bar just evaporate you'll understand why this build is so addictive, ngl I've put probably 300 hours into FL4K alone and this crit loop build is the most fun I've ever had in a Borderlands game period, anyway here's the full setup from the skill tree to the pet to the exact weapons you need to farm
Core Engine: The Infinite Fade Away Loop
The entire build is built around one interaction that's honestly kind of broken when you think about it — Fade Away with the Guerrillas in the Mist augment gives you 8 seconds of guaranteed critical hits on every shot plus some bonus crit damage, and then Head Count refunds action skill cooldown every time you land a crit, and since every shot during Fade Away is a guaranteed crit every single bullet you fire is reducing your cooldown, so by the time Fade Away ends you've already got like 80% of your action skill back and after 2-3 seconds of regular shooting you can pop Fade Away again, it's basically permanent uptime and it feels absolutely unfair
Stalker Tree: The Three Pillars
Your skill points go primarily into the Stalker tree because that's where all the crit synergy lives and honestly the tree is so well designed that almost every skill in it contributes something meaningful to the build, but these three skills specifically are what make the infinite loop possible and you should max all of them no exceptions
Megavore (Capstone)
Gives every single shot a 20% chance to be a critical hit regardless of where you hit the enemy, and I mean this applies to body shots leg shots splash damage literally everything, combined with Fade Away's guaranteed crits you're landing crits on crits on crits
Leave No Trace (3/3)
Critical hits have a chance to return ammo to your magazine, and with the fire rate of weapons like the Monarch on bipod mode this procs constantly, tbh I've gone through entire boss fights without reloading once and that's not an exaggeration
Head Count (3/3)
This is the engine that makes the loop work, every critical hit reduces action skill cooldown and since you're landing hundreds of crits per Fade Away activation the math just works out to near-zero downtime, it's the single most important skill in the build
The Power Inside (Capstone)
Doubles your gun damage while Fade Away is active, and since Fade Away is active basically all the time this is just a permanent 2x multiplier to everything, combine with Megavore and you're looking at damage numbers that make Moze players jealous
You also want to dip into the Hunter tree for Interplanetary Stalker and Hunter's Eye which give you bonus damage based on enemy type and crit damage multipliers respectively, and from the Master tree you grab Ferocity and whatever points are left go into pet damage buffs because every little bit helps when your pet is contributing to your overall DPS
Best Crit Weapons
- Monarch (Assault Rifle) — In bipod mode this thing doubles its fire rate and accuracy and fires a fixed spread, so during Fade Away you're landing like 20 guaranteed crits per second and each one triggers Leave No Trace and Head Count, it's absolutely the best weapon for this build and honestly I'd say it's mandatory, drops from Killavolt on Mayhem 6+ so the farm is rough but worth every minute
- Light Show (Pistol) — 4 projectiles per shot each one can crit independently, so during Fade Away you're landing 4 guaranteed crits per trigger pull and because Megavore applies separately to each projectile you're getting even more crits outside of Fade Away, the DPS output on this thing is honestly stupid and it melts bosses faster than most launchers
- Queen's Call (Pistol) — Critical hits return 3 bullets to the magazine and ricochet to nearby enemies, and during Fade Away where every shot is a crit you literally never have to reload and the ricochets clear entire rooms without you even aiming at anything other than the biggest target, drops from Tyreen so the farm is a long boss fight but the weapon is irreplaceable for mobbing sections
Pet & Class Mod Synergies
Pet Choice: Jabber
Jabber gives you a flat critical hit damage bonus just for having him equipped and his attack command deals surprisingly high damage on its own, he also draws aggro away from you wich is useful because FL4K is pretty squishy compared to someone like Moze or Amara, I mean you're invisible half the time so it matters less but when Fade Away is on its 3-second cooldown window having a pet to distract enemies is genuinely helpful, the Spiderant gives health regen if you're struggling with survivability but honestly the Jabber's damage bonus is just better for this build since your goal is to kill everything before it gets a chance to shoot back
Class Mod: Bounty Hunter or Stackbot
Bounty Hunter procs Hunter Kill Skills on gun damage against bosses and badasses and gives you +3 to the most dangerous game wich is a massive damage multiplier against badass enemies, this is the best all-around option for mobbing and bossing combined. Stackbot on the other hand gives you stacking weapon damage for each consecutive critical hit up to a massive cap and since you're landing nothing but crits you hit that cap in like 2 seconds, it's better for pure boss melting but worse for mobbing where you switch targets frequently and lose stacks, honestly I keep both in my inventory and swap depending on what I'm doing
Artifact: Pearl of Ineffable Knowledge
This artifact gives you stacking gun damage for each consecutive hit on a single target up to an insane bonus and since the Monarch fires like 20 rounds per second you max out the stacks in under a second, it's a quest reward from the Guns Love and Tentacles DLC so you get a guaranteed one but the passive rolls are random and you ideally want magazine size fire rate or action skill cooldown rate as the bonus stats, if you get all three on one Pearl you've basically won the game and should probably go buy a lottery ticket or something
Mayhem 10/11 Boss Melting
On Mayhem 10/11 this build is the undisputed boss killer in the game and I'm saying that having played all four Vault Hunters extensively, the combination of Fade Away guaranteeing every shot is a crit plus Megavore extending that to splash damage plus the Pearl of Ineffable Knowledge stacking damage per hit means you're doing like 10x the damage of any other character during your damage window and your damage window is basically permanent because of the Head Count loop, ngl the only boss that gives this build any trouble is Wotan because of the multiple phases and immunity windows but even then you just wait out the immune phases and melt each bar as it becomes vulnerable, for mobbing it's slightly worse than Amara's elemental build just because you're more single-target focused and need to aim at crit spots outside Fade Away but honestly with Megavore giving you 20% crit chance on body shots you can still clear rooms pretty efficiently by just spraying a Light Show in the general direction of enemies