Here are some possible opposites:
* Krusha (ಕ್ರೂಷ) or Badavara (ಬದವರ): These words mean "ugly" or "unattractive."
* Nishprapancha (ನಿಷ್ಪ್ರಪಂಚ): This word means "plain" or "unremarkable" and can be used to describe something that lacks beauty.
* Vaidhya (ವೈದ್ಯ): This word means "deformed" or "disfigured" and is used to describe someone with a physical abnormality.
* Dushta (ದುಷ್ಟ): While not directly related to physical appearance, this word means "evil" or "wicked" and can be used to describe someone who is considered ugly on the inside.
The best opposite for "sundara" will depend on the specific context and what you want to convey.