The "perfect" character then has to be fit for the purpose you've created them for. Are they portrayed strongly enough to be able to carry out what you want them to do? The reader has to believe the character is at least capable of behaving the way you've set them out to do without there being any "jarring notes" that would make that open to question.
The way the character speaks, even the way they dress, their minor traits etc should all add up to create a composite picture and it should be the one you want to come across. Have your characters ever surprised you with what they've come up with? Mine have! It's a good thing - it shows there is life to them but it can also show you needed to get to know them better before writing for/about them! Sometimes of course in a longer work like a novel you do need to get a certain amount of words written before you really know your characters. But then this is what rewrites (especially of the opening chapters) are for!