Eric Mangini: 0-3 (was intern for old Cleveland Browns before their move to Baltimore)
That fact seemingly means nothing in the modern NFL.
Paul Brown: Genius coach, visionary for the NFL (and the importance of the forward pass - see Otto Graham), grandfather of the West-Coast offense (as Bill Walsh's mentor and Head coach in Cincy). Successful in Cleveland. Team named after him.
Marty Shottenheimer: mildly successful with, and after, Browns.
Bill Belachoke: Great D coach under Parcells. Awful with Browns. "Genius" with Pats (guess the cheating helped a ton).
Bruce Ariens: Great O coach. Awful with Browns. "Genius" O coach after.
Romeo Crennel: Great D coach. Awful with Browns.
What's terrifying: each of the last three made awful coaching decisions, especially in the area of non-expertise, which severely hampered the Browns. Can't blame it all on personnel.