one of a kind; only one and special; someone/something that wouldn’t be substituted by other things/people.
特別, かけがえのない, オンリーワン
平凡, 何の変哲もない, ありきたりな
It’s often used as “唯一無二の + Noun”, and “唯一無二の存在” is a common phrase in particular. While it looks a bit similar to “second to none” (as it says 無二, “no two”), it doesn’t necessarily mean “the best”; it rather describes something/someone that is not comparable with other things/people.
Note that 唯一 (ゆいいつ) is usually pronounced as “ゆいつ” in speech. Similarly, 雰囲気, whose official reading is “ふんいき”, is actually pronounced as “ふいんき”.
I want to found a company that offers one-of-a-kind products and services