Most "promising" fighter who never really blossomed?

[Manju]

For me its Michael Nunn, though perhaps "never blossomed" is not the right phrase. He blossomed then suddenly disappeared, it seems.

But for a very brief shining moment he appeared to have arrived. It was around 1988 and I recall the NYTimes Magazine doing a piece on him entitled "The fighter the great ones don't want to fight"...in reference to SRL, Hearns, Duran, and Hagler.

I don't think its an exaggeration to say he occupied a space similar to RJJ: a big, fast, unorthodox, hard-to-hit and hard-hitting MW with 1-punch KO power. Would've loved to havr seen him develop and fight those greats and RJJ too. But I guess J.Toney should get his due here. Nunn was really something to behold.