S Tier
Snake
Wario
Donkey Kong
Game and Watch
A Tier
King Dedede
Fox
Meta Knight
Luigi
Ganondorf
B Tier
Bowser
Ice Climbers
Ike
Mario
Olimar
Kirby
Zelda
C Tier
Pikachu
Zero Suit Samus
Marth
Toon Link
Wolf
Charizard
Pikachu
Lucario
Lucas
D Tier
Diddy Kong
Falco
Pit
Rob
Ness
E Tier
Link
Yoshi
Ivysaur
Squirtle
Sheik
Peach
Falcon
F Tier
Samus
Sonic
Jigglypuff
Let's see, where was I... I think I'm going to jump around as not to bore myself to death.
1. Jigglypuff shouldn't be at the very bottom. Granted, onstage, she doesn't have that much KO potential because all her Smash attacks are essentially slower and weaker versions of Kirby's with even less range, rest no longer has the punch it used it (plus it's extremelly risky at that), and her throws are average at best but offstage she does a decent job. Fair and bair have a good amount of punch to them and, thanks to her superior jumping abilities, she can follow people decently far off the stage for gimps and recover from dair spikes. If anything, I guess I'd rank her at about the middle of your "E" rank.
2. King Dedede should probably be where you have Wario, to be honest. He's pretty solid when it comes to getting KO's both on and offstage. Onstage, his dtilt and utilt have more punch than some people's smash attacks and, aside from fsmash, his smash attacks aren't that hard to set up. Offstage, bair and fair get the job done and they are made even more effective by King Dedede's awesome recovery. Another thing that should be mentioned that King Dedede's inhale, dthrow, and fthrow do a pretty decent job of getting King Dedede ready to edgeguard. It should also be mentioned that King Dedede has one of the few projectiles that can kill, the gordo, and edgeguarding with waddle dees/doos isn't too hard in some of his matchs ups like against people with tether recoveries.
3. ROB is way too low especially when you consier his edgeguarding abilities are almost as retardedly good as King Dedede's. Overall, I'd probably rate him as the third best character offstage, just barely beating out Kirby. Onstage, his KO potential isn't too shabby either especially since fair, bair, and nair have very little landing lag, the gyro is common place, and his fsmash isn't all that risky as long as you don't use it like a moron.
4. Personally, I'd say that Mario and Luigi are about even KO potential wise. Mario has the superior edgeguarding abilities while Luigi has attacks that KO faster like Nair, fsmash, and the infamous fire punch/surioyuken. Why is Luigi better than Mario then? If you ask me, it mostly has to do with Luigi having better recovery options and better mobility thanks to things like the Luigi tornado because they almost have the exact same standard set ups like using dthrow and utilt to begin strings of attacks. With this all being said, I'd probably move them both to your lower B or upper C rank.
Okay, I lied, I'm bored again so I'll have to come back to this, yet again in another couple of hours.