It is best suited in those environments where complexity is not the key. We've used it fairly extensively in our UNIX to find weak UNIX passwords and in Windows environments too. It's very easy to get hold of as it is essentially Open Source, although a paid version is now available and we are thinking of looking at this proposition in-depth to see if it is viable. We found it easy to install and deploy across our systems. Patching was fairly regular, so we always had the latest version. It holds its own against DES and Blowfish encryption algorithms among many others.
Kali Linux is especially well suited in environments where high security is needed for your custom developed applications. This is well suited for offensive testing your high security in house developed applications. It is also very good for doing penetration testing on in house developed applications and safe guarding them from external attackers. Kali Linux is tough for use as a day to day Linux operating system as this was never intended to be used by beginners and occasional Linux users.
'John the Ripper' being open source was free to use, whereas the others had to be paid for. It was very simple to install and runs against many hundreds of hashes and crypts. It is always developing thanks to large communities on GitHub.
I would say the number one competitor to Kali is Parrot OS. While they both do the same/similar things, both have over 600 pre-loaded tools. Parrot does use some more offer what may be considered a more intuitive user interface. Parrot OS has been around for longer than people think and still has active development a support. But Kali is used more broadly in Training sessions, demos and is considered to be form all the articles I have read, the gold standard for penetration testing and tool sets
Initial stages of figuring out back doors in an application hence making them secure.
ROI is good as it reduces in production security threats by letting us know well in advance.
Entire development team along with its designers get a huge sigh of relief as all security holes are sealed well in advance before going into production.
