Is Violence Jack: Jigoku Gai-hen hentai?
English title: Violence Jack: Evil Town
No
Rated R+ (Mild Nudity) on MyAnimeList and not tagged as Hentai.

OVA · 1988 · 1 episodes · R+ - Mild Nudity
Action, Drama, Gore, Horror, Shounen
The World as we know it has been torn apart shattered by a series of natural disasters that have turned civilization into a brutish nightmare of survival and has left whole cities buried beneath the Earth. It's now a lethal and chaotic place, a place where only the strongest and most savage remain alive. The strongest of them all is a giant warrior known as Violence Jack… Violence Jack tries to avert a civil war brewing among the wretched inhabitants of a subterranean metropolis called Evil Town. Based on a character created by manga horror specialist, Go Nagai. (Source: AniDB)
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