Well, I think it's important to be precise when describing both the best and worst character(s), and never resort to exaggeration. Doing so distorts the ENTIRE rest of the context for discussing all other relative viability within the roster.
I think Zelda is distinctly the worst character in high level 1v1, without question--almost to the point of being a statistical outlier. Her theory and tourney performance seem to support this.
However, Zelda is not irredeemable; her flaws are severe but not fatal.
Zelda has
legitimately amazing tools at her disposal; there are just structural issues that impede Zelda from being able to effectively apply them in a high-level 1v1 environment.
- Zelda dair is so good that I would probably take it on any other character except Cloud and maybe Mario/Rosa/Fox. (Assuming that the frame timings relative to SH stayed the same.)
- The original elevator combo is a legitimately terrifying OoS and combo option.
- D-smash and d-tilt are fast moves.
- Toes and uair allow some of the most brutal punishes in the game.
- Nayru's Love is arguably the best general-purpose reflector in the game; bidirectional, multi-hitting, multi-reflecting, invincible, low endlag.
- Her buffed nair has legitimate combo-starting potential while landing.
The issue with Zelda is that however great these tools may be, she has zero control over the match as a whole--and unlike Ganondorf, she does not constantly exert the threat of being 2 reads away from a stock at any given moment.
I feel like Zelda winning is totally plausible, but requires the opponent make a different sort of errors than we'd associate as needed by low tiers like Ganondorf or Samus. The opponent has to make mistakes not so much that Zelda can simply
punish, but that drop momentary control of the flow of the match and allow Zelda to actually use her (scary and capable) tools.
As Ganon, I need my opponent to make one or two big mistakes. As Zelda, I need them to make a dozen tiny ones.
My problem with Zelda is how baffling her development history is. It was questionable when people learned she had 3 sweet-spot aerials with bad sour-spots. For Dair, not so much, but Fair and Bair? Captain Falcon's late Fair can act as a lingering hit doesn't because his has higher base knockback and active frames while Zelda's has low base and actives. Smash is supposed to be fun and at times, lenient, especially for low level play... And then Zelda comes along with aerials basically asking you to snipe a mile away with a flintlock pistol. By Smash 4, they knew what input lag does which makes spacing thing that more difficult. Her Fair and Bair can keep being high precision aerials, but the sour-spots really shouldn't be that bad. Maybe her sour-spots should do say, 9% with some semblance of knockback and the late hit does 6% with some semblance of knockback. Basically, similar to a Lucas Fair, but with stronger, smaller sweet-spots and weaker, but still stronger than Zelda's sour- and late hits. Oh, look! They're not so heavily punishing while also not having sour-spots that kind of make it seem like they're a bit too good. Basically, her own Dair reward of if you land the sweet-spot, you get massive reward, but if you land the sour-spot, it's okay, but not horrible to you.
Din's Fire is not a recovery move and for covering her recovery, not good since it travels slowly. Why does it make her helpless when used in the air? I'm not sure on this, but I think it also slows down her air speed when used as an aerial... There's no reason then.
The other questionable thing from her development history was her Up and Side Smashes. Those worked fine in Brawl, but didn't for Smash 4's launch until 1.0.6 or something. In other words, they fixed them and they broke them. How do you do that? They worked fine, then why were they broken? How did that even pass Q&A? Game development is a time-consuming and difficult job, but still.
Can she win? Does she have good moves? Yes and yes, but is she a good character? No. Not in competitive play, not in FFA, not in doubles, and for one reason: Zelda's development, character design, whatever you want to call it is just bad. When people said Samus was the worst and I blame memetic culture, the difference is that at least Samus functions in a way that doesn't question why and what the hell were they thinking when designing her. Samus's only real problems are some slightly under-tuned options and some dysfunctional moves. A broken character like Brawl Meta Knight would still be bad game design and bad balancing, but ultimately better character design than Zelda since he just works. He goes beyond what he should be doing, but if we consider Smash 4 Meta Knight as what Brawl was aiming for... then he doesn't have anything questionable. Zelda does. Zelda does to a degree where it's baffling how they though such a character was a good idea and for 3 games without truly addressing her problems.
Those patches that affected her? Fixes not buffs since they returned her Brawl Up and Side Smashes reliability and made Phantom Slash connect properly. The only real buff she had was at launch when they gave her a kill option with Farore's Wind and 1.0.8 when her landing lag was reduced and even then, the lowest is 18 on Dair which does not auto-cancel from a hop and isn't really useful for approaches. Nair does and Nair is, but we're reminded how Falco pretty much stole her Nair while she got a band-aid on hers as compensation. Where's the removal of Din's Fire helpless mode? Where's the reduction in risk for Fair and Bair's sour-spots and late hits? Where's the change to her air acceleration, 0.055, so that it isn't below average, below 0.07? Maybe Ftilt should be a bit stronger, maybe dash attack should be as strong as Peach's, maybe jab and Uair be a bit faster, and maybe her B-throw should kill a bit earlier since she's kind of "magical" and because her D-throw already serves as a combo throw. Maybe U-throw should be altered in a way that it can 50/50 with her Uair and Farore's Wind. Maybe her walk speed should be a bit faster with her Street Fighter cr. LK / Dtilt and maybe her run speed should be 1.4 under Peach and not 1.3 under Dr. Mario and Triple D. All these maybes won't shoot her up to even mid-tier, but they would at least shift her from questionable character design to flawed, but good character design.