Borderlands 3The Tenderizer

The Cartels Event was made permanent on the 24th of July 2021.
It can now always be activated in the Main Menu.

Any of the six Mini-Bosses can spawn at 4 set locations in the Villa Ultraviolet.
2 spawn during the fight with Joey Ultraviolet.

Additionally, a Mini-Boss can spawn after you killed a neon-glowing Cartel Operative anywhere in the galaxy.

Underbosses:
‍FISH SLAP!!!, Franco Firewall, Josie Byte, Roaster, The Tenderizer, Tyrone Smallums