Floyd won 26 of his 49 fights by KO. You know who has more? Pacquiao, and De La Hoya. Guess what, Floyd beat them both by playing defense.
Only other fighters I can think of that would have a chance of KOing Floyd in his weight class would be Sugar Ray Leonard or Roy Jones Jr. Even then, I would put money on Floyd in his prime over either of those two in theirs.
Welterweight fighting is not nearly as much about power as it is with heavyweights like Tyson. You've gotta have power but finesse and fight IQ is way more important. Floyd has all 3 and has been able to balance the lack of power in his later years with his incredible IQ and finesse.
Also funny that you point out your desire for someone like Tyson to KO him. Not sure why you'd hold Tyson, a convicted rapist, in higher regard than Floyd.