crazy smile
A subset of smile where the character is seen smiling out of depravity rather than genuine happiness. Usually depicted either as the more extreme form of smirk and smug or a wide open smile, both with distinctive sharp mouth corners poiniting upwards. Often accompanied with shaded face to emphasize the malicious nature of the expression.
Typically depicted with characters who were either yandere, sadistic, or mentally insane. Also somewhat overlaps with evil smile, as a blend of these smile were also used to display the villiain's sheer cruelty.
See also
This tag implicates smile (learn more).