For Hacker, outside C, he still needs other powerful tools. One of those tools is high-level programming languages like Java, Perl, and especially Python.
Learning more programming languages other than C helps a lot in exploiting and patching application vulnerabilities.
Java is the world's most popular object-oriented programming language according to Tiobe 2016 rankings. It is known as a stable, robust, flexible language with very high security. Understanding security models applied in Java is the fastest way to help you understand the security platforms applied in programming languages.
Perl is a versatile, versatile programming language, some of Perl's features are inspired by C. Python famous for its short, easy-to-learn syntax. Although the syntax is simple, Python can do more things than you think: web programming, big data programming, writing automation tool, ...