There's two so called HBO "documentaries" about Richard Kuklinski, one from 1992 and the other from 2001. And before going into details, let me say right off that, while the initial installment is mildly interesting and watchable, the second is just a sensationalist rehash trying to capitalize once again on the topic.
As to a more detailed criticism, looking just at the 1992 part for the moment the main problem is the utter lack of facts. All we learn for sure is that Kuklinski got convicted on five counts of murder, if I recall correctly, and that it was an undercover agent who's been crucial in this conviction. All (!) the rest is just Kuklinski telling what he wants to tell, including that outrageous figure of over hundred "hits" he is supposed to have done.
Now, I don't know about you but from my experience what a convict tells on camera generally isn't very reliable. He's very likely to lie one way or the other, either to downplay his deeds or to even exaggerate and brag about them, to maybe get more money out of the interview and possibly book and film rights. So for a "documentary", what I would expect is an attempt to link his stories to hard facts, and especially tell us where the police has succeeded in linking him to particular crimes and where not. But exactly this crucial piece of investigation and information is entirely missing.
Instead, we get some reenacted scenes indistinguishably mixed together with fairly random crime scene photographs and press headlines and never learn which is what. In fact, this "documentary" deliberately tries to blur the line between fact and fiction, clearly because it's more about the thrills than real information. The more murders the better, so to speak, no matter if they can really be attributed to Kuklinski.
Hence, regarding the 1992 installment, all I see there is a known five times murderer telling some stories true or not, we never get to know. As that, I'd consider it still having some mild entertainment value while surely not being a documentary. The 2001 installment though is even worse in all regards mentioned above and basically exploitative junk.
So all together I can hardly recommend any of this. If you want to see a real documentary along these lines (i.e. a "serial killer") I'd recommend "Aileen: Life and Death of a Serial Killer" by Nick Broomfield from 2003. Way, way, way better and reputable.
As to a more detailed criticism, looking just at the 1992 part for the moment the main problem is the utter lack of facts. All we learn for sure is that Kuklinski got convicted on five counts of murder, if I recall correctly, and that it was an undercover agent who's been crucial in this conviction. All (!) the rest is just Kuklinski telling what he wants to tell, including that outrageous figure of over hundred "hits" he is supposed to have done.
Now, I don't know about you but from my experience what a convict tells on camera generally isn't very reliable. He's very likely to lie one way or the other, either to downplay his deeds or to even exaggerate and brag about them, to maybe get more money out of the interview and possibly book and film rights. So for a "documentary", what I would expect is an attempt to link his stories to hard facts, and especially tell us where the police has succeeded in linking him to particular crimes and where not. But exactly this crucial piece of investigation and information is entirely missing.
Instead, we get some reenacted scenes indistinguishably mixed together with fairly random crime scene photographs and press headlines and never learn which is what. In fact, this "documentary" deliberately tries to blur the line between fact and fiction, clearly because it's more about the thrills than real information. The more murders the better, so to speak, no matter if they can really be attributed to Kuklinski.
Hence, regarding the 1992 installment, all I see there is a known five times murderer telling some stories true or not, we never get to know. As that, I'd consider it still having some mild entertainment value while surely not being a documentary. The 2001 installment though is even worse in all regards mentioned above and basically exploitative junk.
So all together I can hardly recommend any of this. If you want to see a real documentary along these lines (i.e. a "serial killer") I'd recommend "Aileen: Life and Death of a Serial Killer" by Nick Broomfield from 2003. Way, way, way better and reputable.