BoxRec

Watching this video i realize that I should ask the experts on this forum that is these upsets are really biggest of all the times or there are some others?Love to read an open debate on this. Let see the video first who had not watch it still.
https://www.youtube.com/watch?v=YM1zxKFF1DM

They were all big upsets. (There was a mistake in regard to Tunney-Demspey, the date listed was for the 2nd fight.)

Of course what is the criteria for the "biggest"?

If you are simply going by odds, then of course this is not very accurrate. There have been many fights where the winner was a bigger underdog than say 7-1 which some of these fights were.
I'm guessing that the importance of the fight was being considered.
Also guessing this going by what people thought going into the fight; not having the benefit of seeing how the rest of their careers would unfold.

Some others to consider:
Corbett-Sullivan
Jeffries-Fitzsimmons I
Foreman-Moorer
Holyfield-Tyson I
Sanders-W. Klitschko
Ferguson-Mercer

is deez is or is deez aint the biggest upsets?