People really seem to be missing the very first part of the hint.
"This character is yet another underestimated one, who on the surface seems to be horrible."
Many have mentioned underestimated characters, but not ones that, honestly, seem to be horrible, at least "on the surface."
Alright. I'll play your game. Let's look at things "on the surface" for a bit, without all the bias of a competitive player.
Let's consider some of the most mentioned ones:
Lucas? Does he seem horrible on the surface? A resounding no. Not to mention I'd argue he isn't really that underestimated. I've gotten the sense that he actually isn't doing as well as people expected him to do in tournaments, instead of the opposite. Sure, he has potential to do better, but he's probably high-mid at best, and that's where most people tend to place him.
From a glance, Lucas seems to be incredibly "cheap." He's basically a pumped-up Ness that doesn't suck and is easy to use. You can spam his projectiles all day and rarely if ever get hit due to their high stopping power and PKT2 doing just so much damage and going so far.
Samus? Yes, indeed. She got smacked around by the nerf bat pretty hard in the transition from Melee, and that's the most lasting impression most people seem to have gotten from her, whether they've played her much or not.
At a glance, Samus seems to be a great character. Her moves are quick. Her spikes are easy to land, and her projectiles are great. Her Screw Attack is instant, and her smashes are extremely quick and damaging. You probably won't notice the lack of KO power until you start comparing her with Ike.
Peach? Maybe, not really. She seems kind of mediocre on the surface, but not "horrible" by any means. Yea, she got nerfed as well, but nobody would place her in the same league as the lowest of the low.
Peach seems VERY bad on the surface. Her projectiles take forever and a half to come out and don't travel far, and are mediocre at best. She has no powerful moves that she can reliably use and KO with, and she's incredibly weak, even when compared with other characters, but it just seems to stand out with Peach because of her being... well... Princess Peach.
Yoshi? Yea, definitely underestimated, and he definitely seems horrible at first glance. As any Yoshi main will tell you, though, he has far more merits than most people seem to think.
Yoshi sucks on the surface. I'd clog up the entire topic with the reasons that you'd think so at a glance.
Z.S.S.? Sure, she has some big weaknesses. She's not great at KOing. Laggy grab. Tether recovery (which some people assume makes her recovery bad, which isn't true at all). Not a great approach game (though the stun gun helps). Nevertheless, especially on the surface, she appears to be a fast character with good jabs, a lagless dash attack and good combo ability, especially because of her stunning attacks. I've never seen anybody place her any lower than Low Tier, even on the most questionable of Tier Lists. I would be surprised if #13 were ZSS, as much as I'd like it to be.
ZSS seems devastating on the surface. She's quick, has incredible range with her SideB and Fsmash, her stuff PARALYZES people in place, she is incredibly strong, very quick, tether recovery as well as third jump, etc.
Lucario? Get real. Looks horrible on the surface? Underestimated? Okay, I could see the underestimated part. As others have said, even though he's been doing great in tournaments people still haven't recognized him as one of the stronger characters in the game. Nevertheless, even despite the fact that he seems disadvantaged by an inability to KO until he's taken a good amount of damage (notice I said seems to be, I'm not saying that's necessarily the case), he still seems like a fairly solid character even if you don't know much about him. The Aura Sphere and his pretty decent recovery is enough to ensure that, not to mention his huge, often disjointed hitboxes and his dair.
Lucario sucks on the surface. He starts out HORRIBLY weak, even weaker than Peach or Samus, and the difference isn't noticeable enough at high % due to the perception that at high %, you're supposed to kill. However, you might die first as everyone and their mother is stronger than you, and then you can't kill them! What the hell! And then you get 2-stocked. : \
The story of the scrub Lucario.
Sonic? Despite nearly non-stop argument from Sonic mains to the contrary, many have considered Sonic to be a bottom tier character for a while, mainly because of his lack of priority and inability to KO. Sure, he doesn't really fit the rest of the hint, but I do think you could say that Sonic is a) underestimated and that b) "on the surface seems to be horrible."
Sonic seems like a good character on the surface. He's incredibly quick, which seems at first to make up for all his flaws. You can't edgeguard him due to his stupid recovery, and he's just so gosh darn FAST that you just can't keep up because "YOU'RE TOO SLOOOOOOOOOOW."
Check the earlier pages of the tier list.
Lucario has ALWAYS been in upper mid to low high.
Thats far from being underestimabted like Sonic and yoshi who people still insist suck and are deserving of being in low.
...He's always been mid-mid to high-mid to eventually the bottom of high until recently, and he's just been creeping up slowly until people suddenly went "WTF!? HOW THE HELL DID HE GET SO HIGH?"
He's deserving of much more once you get deeper into him.
What about the Bair?
Or the aura sphere?
Aren't they used as killing moves?
Can't you refresh them with your other moves?
You'll never kill with Bair our Aura Sphere at low % unless you're gimping or your opponent has an obscene amount of damage.
It's Samus. VERY nerfed since Melee, so people chalk her up to horrible pretty quick. Long range game seems to be a strong point, but she also does fairly well in close quarters. I think the air combo hint means the multi-hit u-air and f-air. I say Samus.
Her long range game sucks when you look into it. Everything and their mother goes through missiles, and uncharged shot is too laggy to be spammed.
I think it's Peach too. Maybe I just want her to be next, but it kind of makes sense.
I actually do, too, but it most likely won't happen due to the problematicness of the idea of her "long range game."
I'm gonna go with it being Peach...
Definatly underated due to the large change in playstyle from melee.
Turnips are a great projectile.
Great aerial moves and the float to dair opens up combos.
Also I think her close range game is good.
To sum it all up the biggest trouble with Peach is getting KOs, its all over her forum even.
She's underrated, I'll give you that
But turnips are still horrible excuses for a projectile now. They can't be spammed due to their hour and a half of time needed to pluck just one and Peach's very weak throwing arm.
Her air and close game is good, however.