His English pronunciation is very natural.

He is practicing the pronunciation of Japanese.

This plan is unrealistic.

This product complies with international standards.

That plan is too impractical, it's difficult to implement.

His plan was so unrealistic that no one could believe it.

This design has a unique charm because it is asymmetrical.

That theory is unscientific and has no evidence at all.

I'm troubled by his unproductive attitude.

He is thought to be a very unsociable person.