I agree with exgigirl that neri and clemenza are the best
characters and representatives of loyal soldiers of mike's. i don't believe that either one would have ratted on mike as shown by tom's statement to mike in the study at the end of GFI, " why does neri report directly to you ?" mike knew that he could trust neri completely. if clemenza would have been in GFII, they would have had someone else rat out mike. the scene with neri in the casino taking care of klingman shows how neri handles his business with no ifs, ands or buts. his position in the movie, with the exception of his shooting barzini is sort of taken for granted.