Step 1: Understand the task.
We need the antonym of 'makeshift'. An antonym is a word that means the opposite.
Step 2: Find the meaning of 'makeshift'.
'Makeshift' means something temporary, quickly put together, and not permanent. It is a stand-in used until the proper thing is ready.
Step 3: Decide what the opposite should mean.
The opposite of temporary and rough should be something proper, finished, and permanent. So we look for a word that gives the sense of being fully done.
Step 4: Test the options.
'Expedient', 'substitute', and 'alternative' all carry the idea of a temporary or stand-in choice, which is close to 'makeshift', not opposite to it.
Step 5: Pick the contrasting word.
'Complete' means whole and finished, which stands against the rough, temporary sense of 'makeshift'. So it is the true opposite.
Step 6: State the conclusion.
The antonym of 'makeshift' is 'complete'.
\[ \boxed{\text{complete}} \]