Board Thread:Off Topic/@comment-30582209-20170214224204/@comment-25936766-20170215012218

The main problem with Mary Sues is that people make them unconsciously most of the time, by trying to make a character interesting and original, but not doing so in a good way, making them seem more "special no matter what it takes" than anything.

And depending on one's writing skills, they can become true Mary Sues. Since 90% of all fanfic writers suck, that is nearly-always the case.

Trying too hard to make an OC interesting leads to Sues...but trying too hard not to make one can lead to an Anti-Sue, which generally is just boring because they got almost nothing to make people get interested.

The best way to avoid making a Mary Sue is, design-wise, 1) to not make them "too special" for the work in question (say, fairies in a CSI fanfic) unless it's supposed to be the point; 2) not add too many things; 3) Not make them better than most of the cast, especially the "big bosses", in terms of skill, power and/or smarts.

For the greater most part, however, Sueness depends entirely on their creator's writing skills. For example, making characters give nothing but praise for the OC or side with them or their opinions, even if it'd be OOC for them, would be bad writing, and would make an OC a Sue, even if design-wise they avoid most traits.