How bad is it? It's so bizarre it's terribleness is hard to measure.
Should you see it? Only in the original version "Welcome Home, Brother Charles" and only if the review sounds like something you'd watch.
The version of this film currently on video, called "Soul Vengeance," is heavily edited, removing the only reasons for watching this film, so beware.
A black man in prison has scientific experiments done to him and gets castrated, which turns his penis into a monster that can change size at will. When released from prison, he uses it to exact revenge, seducing the men's women (apparently the sight of his monster penis is mesmerizing) and killing them. In the last scene, he strangles a man with his penis, which is now several yards long. Whether it's all a dream sequence, some magical or supernatural occurrence or a freak of misguided science (or nature) is left to the viewer - if the viewer cares.