Biggest weight difference between the fighter scoring the knockout and the knockoutee?

It amazes me how some view Leonard as a prima donna ,
or a runner. He COULD use movement if he needed too
but most of his career he was aggressive, and looked
to hurt his opponents, and if he hurt them, they usually
didn't survive.
Leonard was a absolute beast in the vast majority of
his fights.

 

He beat a couple of guys north of 200 for whatever it is worth.

 

Dempsey v. Willard, approximately 58 lbs.

 

Well this is kind of opposite what OP intended, but within the strict confines of the thread title:

Sugar Valuev had about 195 pounds over a guy he KO’d early in his career named Alarim Uysal.

 

Fitzsimmons v Millard Zender in 1892 Fitzsimmons gave up 140 pounds(160 to 300). This was Zenders only pro fight. Actually his only pro round cause it was a 1st round KO.

Hes also gave up 90 against Dunkhorst who was pretty solid and 75 and 70 against other debutees Charles Puff and Abe Coughle. Neither Puff or Coughle fought again.

Fitz is probably the answer here because he could maintain ATG HW power at the lowest weights anyones ever maintained it.

Childs KO'd Armstrong and stopped him twice but there are no weight numbers for either fight. Childs was 5 ft 9, Armstrong was 6 ft 4.