So what would the weakness of the INTJ be?Evil INTP guess
Milton Waddams (red swingline stapler)
Clyde Shelton (Law Abiding Citizen)
The Puppet Master (Ghost in the Shell)
This class of criminals are about undermining a system rather than a specific person. They see that there is something wrong with society, or a way of doing things and so they study and create ways of interrupting and dissolving these systems. Their execution strategy is through intermediaries: working only through messengers. It's extremely rare to find an INTP personally killing someone except in those cases of personal retribution or personal vindication.
The difference between an INTJ and INTP criminal is that an INTP will give the current system a try and then find that the system's bad parts outweigh the good parts. The INTJ criminal will reject the current system an try to install a new one of their design. In short general terms, INTP will try a bad system, INTJ will reject it on definitive grounds or on principle.
The aftermath of a successful plan is somewhat different for the two. I suspect that the evil INTJ will want to rule this new paradigm and therefore will show their face at some point for the public to recognize their new leader. The evil INTP will be extremely difficult to catch because they wouldn't mind being the janitor or secretary of the new system, therefore never showing their face. To catch the evil INTP is to apply pressure and monitor movement patterns and resource usages. The general weakness of the evil INTP is love.