C has no support for closures, no guaranteed support of tail calls

There is no way to portably inspect the call stack. Hence, you cannot code something like GNU backtrace or longjmp/setjmp in portable C. Also, coding precise garbage collectors is very painful.

There is no ABI, every vendor made up their own. Higher level constructs have to be manually created or third-party libraries and other solutions used.

There are no namespaces, so it's easy to pollute global namespace and wreck something up.

Finally, C doesn't support exceptions and object oriented programming.