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Nightmare Fuel: Cyborg 009
In "Little Visitors", we get to see the result of the alien slavers attacking Shanghai... repeatedly. After destroying the city, they rewind time just so they can experience the 'fun' of slaughtering everyone again.
"Frozen Time". Joe gets stuck in his Super Speed mode. He can see everyone, but can't interact — simply touching them while constantly acclerating could be catastrophic. The effects this hason his psyche are swift and brutal.
"Black Ghost Lives!" offers a look into the sort of experiments the organization ran on the cyborgs when they were first converting them. It's just as fun as it sounds.
What happens to Pyunma in "Old Friends" ( a terrible beatdown from a Brainwashed and Crazy friend and later a heartbreaking Shoot the Dog moment, and the fallout during "Nightmare of Van Bogoot" where his body is almost torn apart.
How Nicholas died in the Psychic Assassins's arc. Having your neck and maybe all of your limbs snapped via telekinesis is a TERRIBLE way to die, and for worse the Cyborgs try to help but even with all their powers, they can't do anything.
In the 1979 arc, Jet has an arm ripped off him. If it was bad enough to see him getting a leg almost destroyed in the 2001 series twice, then this is said scene taken Up to Eleven. Specially when there's a close-up to the poor guy's horrified, pain-stricken face...
See that allusion to Pyunma's Near Death Experience in the 2001 series? It's much, MUCH worse in the original manga. As in "mangled to the point all that's left is his HEAD" worse.