perhaps "grimace"
Frown
I think sneer's antonym may be: friendly...?
A synonym for the word grin is smile. An antonym for the word grin is frown. Synonyms: gleam, glow, grin, laugh, radiate, shine, smirk Antonyms: frown, scowl
The word smirk is a noun meaning sly smile. Synonyms for the word smirk include beam, grin, leer, simper, grimace, grim, sneer, visage, and smug look.
Smirk does not have a suffix. Usually words with only one syllable, don't have a suffix.
confident smile, beam, grin, leer check thesaraus.com if you want some more
Grin.
smirk
The prefix of the word "smirk" is "sm-" which means a slight curling of the lip, often indicating amusement or smugness.
Josh had a smirk on his face when he got a B+ on his test.
Grin or smirk
smirk