This is a list of the characters weight, in comparison to each other. Mario is weighted at 1.0 and Bowser is around 1.1 that means that Bowser weighs 10% more that Mario, HOWEVER, it does NOT mean that an attack that kills Mario will kill bowser if he has 10% more damage. knockback is based of of other situations as well as weight. BUT this list is 100% accurate.
Bowser 1.111
Donkey Kong 1.091
Snake 1.076
Dedede 1.071
Charizard 1.061
Ganondorf 1.056
Samus 1.051
Yoshi 1.045
Wario 1.045
R.O.B. 1.040
Ike 1.035
Captain Falcon 1.030
Link 1.030
Wolf 1.020
Lucario 1.010
Ivysaur 1.010
Mario 1
Luigi 0.995
Sonic 0.985
Ness 0.980
Pit 0.980
Lucas 0.980
Diddy Kong 0.975
Toon Link 0.970
Ice Climber 0.970
Peach 0.960
Marth 0.944
Sheik 0.935
Zelda 0.935
Falco 0.919
Olimar 0.919
Zero Suit Samus 0.914
Fox 0.910
Pikachu 0.904
Meta Knight 0.904
Kirby 0.899
Squirtle 0.884
Mr. Game & Watch 0.884
Jigglypuff 0.849