Disad

disad, disads, n. ("diss' add") 1. a stat or characteristic assigned to a character which is designed to be detrimental to the character's success, or would otherwise be perceived as negative; usu. as payment or trade-off for an advantage, or positive characteristic (see merit); abbrev. of "disadvantage." 2. a general description of anything negative. Ex:One of the disads of Mike's game is that Adam will show up. See flaw. [GJ1]
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Addendum: I can shed light on the etymology of the word "disad," which you list as synonymous with "flaw." The word came from the Champions superhero role-playing game, where the flaws were called "Disadvantages." The word became shortened and was later applied to many other games and gamer experiences. [EDE]