Of all time?
It sounds like a bold statement, but those quotes are pretty telling. They come from reputable sources.
Ali fought Foreman, Frazier, Liston, Cleveland Williams, and a slew of others known for their punching power.
Ron Lyle fought Foreman, Oscar Bonavena, and Gerry Cooney,* who all are known for their punching power.
Larry Holmes fought Cooney, Ken Norton, and Mike Tyson, among others.
*Don't laugh...Gerry Cooney could punch. George Foreman said he was the hardest puncher he ever fought: George Foreman on David Letterman