Welcome to tag of the day, my new daily* series where share a tag† I found useful but underutilized in generations and explain how/why you should use it (and actually wrote up most of last month).
Smug
Not immediately obvious as a valid expression tag, but one that is recognized by models built on SD (1.5, XL, PDXL, likely ILXL but haven't tested it). Besides the obvious use of making a character’s expression be smug, this emotion has the advantage over most emotion tags of rarely coming up super exaggerated like many emotions do, so it’s useful for getting a character to display some emotion without needing to play with weights.
Possible Pairings: Crossed arms, looking at viewer, smirk,
*Will not actually be daily.
†May not actually be a single tag