As everyone knows, a good character needs to have many strong qualities such as a unique personality, particular capabilities, and especially a few weaknesses. I've seen many examples of fan made character backstories going around, but I've noticed a bit of a pattern with some of them, that pattern being that a few of them can be pretty long. I'm not looking to judge anyone, but one of the tips I can provide for this is to keep it simple. In other words, make it so you can sum up your character in one sentence. For example, if you were looking to describe Twilight, you could say this: "An intelligent pony princess who loves to read books." Those who hear this basic description are able to build upon this view and develop their own interpretation of the character much easier. But that's not to say you should make your character bio too short, just try to write a summary that expands on information one piece at a time, rather than trying to introduce new information all at once. So in conclusion, try to keep things simple, because basic concepts are much easier to develop than complex ones.
So do tell, in your own opinion, what do you think makes a well-written character?