I have been thinking about the complex and kind of baffling dynamic that Verkhovensky and Stavrogin have going on between them and I finally think I have it pinned down:
Verkhovensky holds Stavrogin in a checkmate, and Stavrogin holds Verkhovensky in a chokehold.
Throughout the book, Verkhovensky does increasingly dangerous things to ensure Stavrogin is tied to him, bound both with some sort of beneficial, parasitic relationship, as well as simply with fear of imprisonement or death. Everytime Verkhovensky does something, he makes sure to work on the two different sides of the coin: for example, when he orders Fedka to do away with the Lebyadkins, he not only relieves Stavrogin of two burdens at once (being married to Marya and being blackmailed by the captain), he also makes sure he has an alibi (a night with Lizaveta, which in and of itself is also what Stavrogin was after the whole time). And then, he makes sure that everybody immediately knows that Marya was Stavrogin's wife and that he benefits greatly from her death. Due to all of this, Stavrogin is trapped in one position and cannot make a move without stepping on Verkhovensky's toes and putting in motion a series of events which would be highly unfavourable to himself.
On the other hand, Verkhovensky is also risking quite a lot in pulling all of these stunts after the other, and sure, some of them are mostly out there because he wants to discredit his father, but the most dangerous things are always done with Stavrogin in mind. And while Stavrogin is absolutely being complicit by knowing of everything/almost everything that will take place and doing nothing to stop Pyotr, he is also not guilty according to the law (someone please correct me on the penal law in imperial Russia) - but Pyotr is. Just as he is spying on everybody in the town, he could likewise be spied on, or even simply overheard by literally anybody. Fedka could denounce him for paying him for the murders, Mavriky Nikolaevich could physically harm Pyotr (or even simply kill him) for entangling Lizaveta into it, Shatov could kill him during their confrontation... he is risking quite a lot, much more than what is comfortable for him. But he continues to do everything again and again because he is held in place by Stavrogin, who deliberately doesn't tell him: no.