So, spoilers, you'll have to die to get the Borderlands 3 Hazardous Sellout legendary. It'll be worth it though as you'll respawn a few seconds later with a very handy gun. There are other options, but only death will get you the gun and it's a small price to pay for such a useful tool.
In order to get the Borderlands 3 Hazardous Sellout legendary, you'll have to first complete a mission called "The Family Jewel" in the main quest line Voracious Company. Once that's done you can head to Eden-6 and find Ambermire (which won't unlock until you do) and face your fate.
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Once there, Troy and Tyreen will contact you with a side quest called (wait for it) Sell Out, asking you to kill yourselves in their specially built death trap for more views on their Children of the Vault channel. Just follow the waypoint, and you'll find it in the middle of Ambermire.
The Calypso Twins promise to give you a sweet new gun if you go through with the self-execution, but you also have the choice to ignore their requests and destroy five of their surveillance cameras in the area to reduce their viewer count instead.
This is obviously the more heroic of the actions, but doing so will lock you out of the chance to get Hazardous Sellout for good. To kill yourself, simply enter the death machine and press the button, and you'll simply respawn at the nearest fast travel station only a few dollars shorter than before.
The gun itself is one of the best Borderlands 3 legendaries in the game, making this well worth the self-sacrifice, though be warned that it's pre-built with the voice of Tyreen Calypso herself, who spouts off one-liners every time you get a kill.
Still, Hazardous Sellout fires off three rounds of potent contact explosives with every shot, and boats a +100 buff to Splash Damage Radius, with the option to alternate between both Incendiary and Corrosive elemental round. As far as Borderlands 3 Legendaries go, then, you'll want this one for your inventory.