Quick thoughts on bottom 15 right now maybe to stir something up (I think this is what would be D tier):
Mewtwo and Mac both have some powerful things going for them and then they die. Jigglypuff also dies, but has much less going for her in terms of neutral and advantage. Ganondorf's 2x higher reward doesn't matter when he can't get in and is so slow as well as easy to hit, an absolute noobslayer character though so may still have skewed opinions. Might prove to be worse than Jigglypuff eventually. Palutena has a pretty good neutral because of her mobility, dash attack and aerials but she also has terrible CQC, fairly useless specials and tilts, as well as slow and punishable smashes. No reliable way to get kills and she's tall and light, definitely mid tier with customs due to superspeed and the dthrow uair combo she gets. Zelda also has a bunch of dysfunctional attacks that don't have much utility, and while she can close off stocks better than Palutena her neutral is way worse due to her fair, bair and poor overall mobility. Tall and dies early as well.
This is where my confidence drops a little bit, Charizard has good OoS options in up b and up smash (very powerful but not super fast) and a kill throw, but his aerial mobility is pretty terrible and while he has a couple decent autocancels and two mid-air jumps he can't land with anything that wouldn't be risky. Pretty much the same with Bowser except his OoS and landing options seem a bit weaker and his kill potential and damage is greater, in particular he has great tilts and a command grab. Shulk has terrible frame data but quite a lot of safety, yet it doesn't ultimately matter when he can't keep people off of himself and Monado Arts tend to have just as much drawbacks as benefits. Gimpable recovery and struggles to kill. Marth is better than Lucina by a couple spots mainly because of the clutch factor of fsmash. Both characters are a lot better after the last few patches, but still I can't see how either of them kill reliably. Neither gets anything directly off of their very low damage throws either.
Falco, Kirby, Dedede and Samus I think all have something going for them that more or less separates them from the rest. Falco and Kirby have great CQC, just struggle moving around due to their slowness and effectively lack a projectile. Kirby also benefits from his size. Dedede, in the context of being a superheavy, is special for his multiple jumps, disjoints and a lagless aerial in nair making landings relatively easy, as well as a projectile (slow gordo is definitely not useless). Pretty good recovery as well, and survives forever. Samus has 40+% combos out of dash attack with her great aerials and also gets a lot of mileage off of zair, max range ftilt and CS. As such she has a great midrange game and also decent CQC options despite her bad grab with her fast and safe jab 1, dtilt and up b. Good survivability as well, and I think the only things that really keep her down are her trouble resetting to neutral and dealing with pressure because of her slow and punishable grab, floatiness and height. "Decent CQC" also isn't good enough vs heavy, constant rushdown, although on the other hand you can't hope to just outspace Samus and keep her out and win. The most underrated low tier in my opinion because too often she's placed dead last or bottom 3, and there's a ton of misconception about her attacks being bad when they're actually really good (like fsmash and dash attack).