Violence Jack

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 , who quickly becomes a rival to Jack and the two clash multiple times. Jack fights several other enemies throughout the manga and OVAs.

(Source: Wikipedia, Go Nagai Wiki)