ಠ_ಠ, otherwise known as the “look of disapproval,” is a character sequence commonly used as a reaction emoticon to express one’s disapproval or disbelief.
The unicode character “ಠ” comes from the letter “ṭha” in Kannada, one of the major Dravidian languages of India that is influenced by Sanskrit. Despite its origin, the character has been used as an emoticon primarily outside of India. According to Lurkmore Wiki, the earliest use of ಠ_ಠ began on the Japanese imageboard site 2channel and eventually spread across other languages, most notably on 4chan.
The emoticon is most commonly used to express disapproval or disappointment.