So obviously if bangs are so prolific that 98% of posts should have them, then a "no bangs" tag WOULD be appropriate. And that tag should NOT include images where the bangs are pinned back or whatever it should be reserved for images where the character has NO BANGS, such as someone who lets their hair grow naturally and does not cut it at all, for example.
If it's SO uncommon for characters to not have bangs, due to how ubiquitous bangs are, then obviously having NO bangs would be noteworthy enough to deserve a tag. That is what I am looking for and I should not have to sift through a million images of untagged specific bangs types to find it, nor should people be forced to figure out what specific types of bangs a character has in order to tag it, and presumably there would be infinite possible styles of bangs, making it likely that they may not find an exact match and thus wouldn't tag it.
If we are worried about people forgetting to tag "bangs" every time because bangs are so ubiquitous, then we should obviously just have a "no bangs" tag for images where the character has NO bangs.