In my opinion Lionel Richie is one of the best funk singers.Yes he is a Sugarfoot Booner student

but in my opinion he took the best elements from Sugarfoots singing style and made it his own.

Songs like Look What You've Done To Me ,Fancy Dancer,Slippery When Wet,many others.Lionel owns that owww vocal thing.

But in the 80's his singing on funky jams like Don't Stop,Cant Slow Down sounds like he's struggling to keep the pace with the beat.kind of whimpy thin vocals.

Lionel didn't abandon funk ,even though there was larger quantity of slower songs but with his uptempo stuff he continued similar path to sophisticated rnb funk that Commodores started doing on their In The Pocket album.