Oh - I did go with pentesting and ethical hacking for a while. For hacking, unfortunately or fortunately a wide variety of languages is needed. Again, depends on what you want to do. All hackers at least have a moderate understanding of scripting languages such as Python, Perl and .... as they are absolutely crucial to automating the programs that they use. For coding payloads, making viruses and hacking in general, all companies if not most look for experience in C as it really goes to the deeper levels of computer science and binds quite well with hardware like Ras Pi, Arduino and ...
BTW, if you are interested, Null Byte is the best source for free hacking tutorials and another website which I will dig out of my bookmarks.
So in overall, alot of experience in languages like C and oh I nearly forgot =- networking - a MUST. TCP/IP, Stacks, Packets and ...
ResourcesNull Byte - hacking in general. LOTS OF INFO
Cybrary - free video tutorials and partnership with Cisco and more =- pentesting, networks and more
Check them out!
(Phew)