What real world tasks can Lisp do that C cannot?
There are no "real world tasks" that Lisp can do that C cannot, because of two things: 1) C coders will emulate Lisp features when required, even going as far as embedding an actual Lisp. 2) The question is poorly stated. Someone that shows something Lisp can do that C cannot will just be told that the thing shown is not a real world task. Example: Lisp gives you dynamic typing, garbage collection, S-expressions, macros that actually work, pattern matching, etc. Answer: these are not real world tasks, show me a real world task.
Turn the question inside out. C coders will sometimes embed a Lisp to overcome the limitations of C. When was the last time a Lisp coder embedded a C? (Hint: Lisp Machine C was created to be able to run C programs, not in order to overcome some limitation in Lisp). You should ask yourself if you want a language so limited that you have to emulate a better language, or if you just go with the better language from the start. What real world tasks can C do that Lisp cannot?
Your question is also deeply stuck in 1990s culture. Have you tried to accomplish some real world tasks in C today? Look at what kinds of programs most people around you are exposed to every day, that's the real world. Have you tried to make a web site in C? Where's that smartphone app written in C? If these exist, they are curiosities, like those programs people write in pure assembler just for the heck of it. The world has moved on from C.
The real wonder of Lisp is how it transforms your thinking about programming, and it has the taste of freedom.