Considering his supporters claim him to be one of the greatest feathers ever, then make a long, long list of excuses why he lost to MAB, it would be Naseem Hamed.
Bob Fitzsimmons Jim Jeffries Stanley Ketchel Jake LaMotta Bernard Hopkins Pernell Whitaker (above 140)
I’m not one of those Pacquiao is the GOAT guys - but honestly he can’t really be overrated… his achievements are so incredible it’s kind of silly when you sit back and look at them. Even if we add the * of PEDs, a bunch of other fighters who have been caught with PEDs have nowhere near Pacs achievements. The rest of your mentions I think you could make a case for.
Larry Holmes, without a doubt. Barely beat a 190 lb Tom Prater who was a half hearted fighter at this point (He was my coach at Indy PAL in 77-78, so I saw this first hand), barely beat Norton, Weaver and got a ref assist against Snipes and judging assists with Witherspoon and Williams (both of whom I thought beat him clean and neither was in his supposed class) and then got slapped around by a blown up Spinks. Loved his professionalism and discipline and thought he maxed out his talents and like him personally, but rating him Top Three all time is dizzingly out of place.