In the first examples(Python, Ruby, R) the exponential operator has higher precedence, we can see that is the case for Python from Python Operator Precedence, Ruby from Ruby Operator Precedence and R from Operator Syntax and Precedence. So the exponential operator will be applied before the unary minus will.
It is worth it to note that as Vincent Zoonekynd points out Excel actually behaves the way the OP expects in this case and so depending on your background the problem may actually not be as obvious as a lot of the comments purport.
The misunderstanding here appears to be that you expect the -
to be part of the number, which it is not. The -
is actually an operator which is applied to the number just like exponentiation.
In C you are entering a negative number and therefore there is no operator precedence to deal with. For reference here is C operator precedence table.
So you are comparing two different things here, if you did something in let's say Python you would see a similar result:
>>> x = -5
>>> x**2
25