The criteria is simple. The grading is based on the their performance and the level of opponent they faced. Timing of fight, activity, accolades, and age of opponent is factored in as well.
Canelo
vs Scull- D-
vs Berlanga- A
vs Munguia- B
Terence Crawford
vs Madrimov- C
vs Spence- A+
vs Avenysean- B-
Jaron Ennis
vs Stanionis- A
vs Karen rematch- C-
vs Karen- C
David Benavidez
vs Morrell- A
vs Gvozdyk- C-
vs Andrade- A-
Gervonta Davis
vs Lamont Roach- C-
vs Frank Martin- A
vs Ryan Garcia- A+
Inuoe
vs Cardenas- B
vs Joon Kim- B
vs TJ- B
Jai Opetaia
vs Nyika- B
vs Massey- B+
vs Briedes- B
Shakur Stevenson
vs Padley- C
vs Artem- C-
vs Edwin DLS- F-
Teofimo Lopez
vs Arnold Barboza- A-
vs Claggett-- C-
vs Jamaine Ortiz- C-
Usyk
vs Fury 2- A+
vs Fury- A
vs Dubois- B
Vergil Ortiz
vs Madrimov- A
vs Bohachuk- C
vs Dulorme- B+
Devin Haney(Ryan Garcia fight is void)
vs Jose Ramirez- D-
vs Prograis- A
vs Lomachenko- B+
Bivol
vs Beterbiev 2- A
vs Beterbiev- B
vs Zinad- B+
Alberto Puello
vs Sandor Martin- C
vs Gary Russell- A
vs Madera- B
'
Brian Norman Jr
vs Cuevas- B+
vs Santillan- A
vs Quinton Randall- C-
Bivol
vs Tiger Paw Artur Rematch: A-, first man to convincingly beat the Russian-Chechen beast many competitive rounds
vs Tiger Paw Artur: B-, gave away the rounds 10 and 11 by sticking to the game plan instead of boxing to take these rounds
vs Zinad: B, touched up in the process of rushing the KO of an overmatched opponent