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Nightmare Fuel: Tex Willer
What Tex did to Fred Brennan, the last survivor of the gang that caused a smallpox epidemics among the Navajos, killing Tex's wife in the process. After isolating him on his own floating casino, Tex had him wake up in the middle of the night at the cries of people scared by smallpox, placed a skeleton at the rudder to get him even more terrified when he tried to investigate who was shouting, set the ship on fire (at this point Tex's pards were wondering if he was overdoing it), and then sank it in an area filled with sharks.
Tex's whole Roaring Rampage of Revenge, when you think it through: Tex is the Fastest Gun in the West and a Scarily Competent Tracker, and was at his most furious. The lucky ones, that Tex couldn't afford to torture as he wished, got shot. The unlucky one, Higgins (the guy who delivered the infected blankets that caused the epidemics), was forced to walk in the desert until midday with the head uncovered, beat up within an inch of his life, and then left there to die.
And the epidemics itself. It's not shown, but the idea that someone would do something like that just to kill one man...
Padma's illusion attack on Mefisto, including having him attacked and swarmed over by dragons, serpents, mice, large spiders and other unpleasants critters until he's gone completely insane. Good Is Not Nice indeed.
The worst part? That's him holding back: before dealing with Mefisto he had asked to a mystic force if he was allowed to kill Mefisto and was told no, implying he can force people to just drop dead.