Can’t say that I care much for Action 799 (March 2003), by Kelly and Carlos Meglia.
The art has a lot to do with that. Although I do have to admit that it suits that story, in which a giant ape runs wild in the streets. It just doesn’t appeal to me.
Between the apes and the obvious mental manipulations (Superman does not really get turned into a chimp in torture, it’s just a vision he is sent), Superman’s first guess is that Grodd is behind this. But the Flash lets him know this is not true, and Superman follows the mental trail to Chicago.
The “villain” is really Hector Hammond, who is being drugged and tortured by the relative of one of his victims. His actions were a cry for help.