When a former employee made his own peepshow machines, Underhill built a massive car bomb and blew him to pieces. He then brought the guy's splintered bones back to Thevis, who joked about turning them into a paperweight. On another occasion, Thevis lured a rival to his warehouse, shot him in the head, then accidentally locked the corpse in his car with the keys in the dead man's pocket, prompting slapstick panic.
But you can't remain a rich porn warlord forever. When he was arrested for arson (his usual method for dealing with competitors), Thevis became paranoid that Underhill would rat him out. From prison, he sent numerous hitmen after Underhill, which turned out to be a mistake. Underhill survived the attempts on his life, but sending assassins after someone tends to hurt a friendship. He agreed to become an FBI informant, wore a wire, and took Thevis down.
Realizing he might not talk his way out of this rap (because he had just talked his way into it), Thevis used his massive wealth to buy enough favors to escape prison. This sparked an enormous manhunt, landing him on the FBI's 10 Most Wanted list. Thevis was mere inches away from a new life, with a million dollars in jewelry and one of his mistresses on his lap. But then he found out Underhill had used the escape to sue Thevis for his fortune, figuring one of the most wanted men in America wouldn't show up for the court hearings.
Thevis turned the car right around and started hunting Underhill, who was days away from disappearing into witness protection himself. With the help of a dirty cop, he caught up with Underhill as he was trying to sell his house to a local grocer. Thevis murdered both men with a shotgun, then stuffed them into trash bags. But as the previous hitmen had learned, Underwood was too tough to just drop dead. Clinging on to life until his wife found him, he fingered Thevis for the murders with his dying breath. The porn king was arrested a few weeks later at a bank, and while he denied all wrongdoing, 1,000 boxes of evidence, 300 witnesses, and his best friend turning on him were pretty damning. He died in jail in 2013.