Tentang
Half-man, half-giant; Jack is large and incredibly strong and wields a large jack knife. Jack scours the underworld and lends his strength to good causes, protecting the weak and bringing justice to the post-apocalyptic world.
Violence Jack is a giant, 10 to 12 ft seemingly unstoppable inhuman man, who after been uncovered from under some rubble, wanders the wastelands of a destroyed post-apocolyptic Kanto, which had been destroyed by the "Great Kanto Hellquake". Kanto is now ruled by a psychopathic, samurai warlord named the Slum King, who quickly becomes a rival to Jack and the two clash multiple times. Jack fights several other enemies throughout the manga and OVAs.
It was later revealed in the manga that he was the reincarnation of Akira Fudo/Devilman.
In CB Chara Go Nagai World, it is revealed that Jack is Akira Fudo (Devilman) after his battle versus Satan.
(Source: Wikipedia, Go Nagai Wiki)