Here's "Twintale"---though I cheated a bit and thought what if this is a mistake and it's meant to be "Twintail"? He's just your average everyday Kamaitachi...
Greasel - "Weasel Knievel" (or "The Yokai Yanki", as he'd be known in Japan)
Greasel is a humanoid weasel, kind of Tex Avery-ish, with a thin lower body but broad chest and shoulders. Think like Talbain from Darkstalkers, but a weasel. We have a character that appeals to the inflation fetishists, so why not a furry too? He's got a delinquent slouch to him and dresses like one too, basically he has a jacket like Jotaro from JoJo and a similar hat that obscures his eyes (does he wear a mask? nobody knows!), though the top of his hat is ripped and a silver sickle-like Birdie-style mohawk pops through. He has white bandages wrapped around his waist, but outside of his open jacket he's naked. But he's covered in fur and isn't anatomically correct, so it's no big deal! Instead of arm ARMS, he has two ARMS-powered tails. He kind of sounds like an evil Elvis.
Figure skating flowers. Obese otherworld horrors. The living dead. What would once raise an eyebrow has since become part of the norm within the ARMS World, and the mysterious creatures that once were spoken of in hushed tones have since become contributing members of society. One such species is the Kamaitachi, humanoid weasels with twin tales. Once they were feared and hunted down by the elite ninja, but that was hundreds of years ago and such violence is all but forgotten---now they live and work alongside everyone else!
Greasel is a Kamaitachi who doesn't like to be lumped alongside everyone else. That's boring. He's a notorious biker, the leader of the "Evil Weasels", and he's a bad boy with a bad-streak as long as his ARMS-powered tails. He channels this meaness somewhat constructively by competing as an ARMS Fighter, and he's quite the controversial figure. He doesn't merely play a heel like Big Bengal does for the benefit of the fans, Greasel is a dyed-in-the-wool heel who is as every bit as sadistic and nasty as he is outside the ring as he is on the inside. He does whatever it takes to win and isn't necessarily above playing dirty, but for the most part he has a twisted sense of that fighting spirit. Women love that about him. When women publications rank the male ARMS fighters, he consistently ranks at the top in popularity. He's not exactly thrilled at that, though, because he doesn't have any goodwill towards his fans and finds them annoying. "Don't cheer for me, bastards!" he can often be heard shouting.
Nobody knows why Greasel is such a delinquent. He grew up in a happy home under loving parents, who happened to be high-ranking Shinobi, and as a child attended Ninja School where he excelled with high grades rivaling that of Ninjara. The two of them were in fact best friends in Ninja High School, but an unknown falling out between the two turned them into fierce rivals. It's not uncommon for their fights to spread outside of the ring, though the fans love when this happen as they really go all out then. While Ninjara continued his studies at Rasen University, Greasel took to the road and acquired a massive amount of traffic violations---violations which he continues to pay off to this day with his prize money, though he only racks up more and more.
In the end, perhaps Greasel is just a natural-born rebel? Maybe he wants to revive the monstrous image of the Kamaitachi, and dislikes his clan allying themselves with their former enemies. Whatever he's looking for, maybe he'll find it one day down that long, winding road called life.
Greasel slouches when he moves (usually holding his hands in his coat pocket) but is quite fast, able to weave in and out and being low to the ground can make him hard to hit. His ARMS Girth is on the lower end of the spectrum, and his Throw is weak. As you can imagine rather than using his arms he uses his twin tails as his ARMS, though they work more or less functionally the same as regular ARMS.
Greasel's first Ability is "After Image", a move he picked up in his ninja days---when Greasel dashes on the ground or in the air he leaves behind a trail of afterimages that can confuse the opponent. Though your ARMS will always target the real Greasel, it's a nice way to play mind games with your opponent as they may mess up their ARMS trajectory by accidentally curving towards one of the fakes. It's one of those Abilities that is less an Ability and more a way to mess with your opponent's head and think twice about what you're up to. The afterimages are a few frames slower than the real deal, so if your opponent's eyes pays too much attention to them they may miss the tell of the real Greasel launching an attack. Pretty sneaky!
His second Ability is "Revv Up". If you hold the dash button, Greasel will turn into a spinning ball---hmm, I've seen this somewhere before? If you let go of the dash button after charging, he'll shoot forward in the direction you're holding. This can't hurt the foe, but it's nice to quickly avoid them. He's vulnerable while charging, so use it when you have an opening, and either make a quick escape or charge in! You can jump out of the dash quite easily and then attack and, oh, did I mention he leaves After Images while dashing in this way too? There's another more advanced technique available here too, known as the "Rev Cancel". If you release dash and immediately press jump within a few seconds, Greasel will quickly exit in a jump---but he'll leave behind a fake Revv Up ball made of compressed air, which will shoot off. This ball of air doesn't actually do anything, but your opponent may not realize what has happened at first and temporarily be confused as they mistakenly target the ball. Yeah, Greasel doesn't cheat necessarily---he just loves to mess with the opponent!
Greasel's signature ARM is the Slickle, a very slick, uh, sickle. In the past Kamaitachi were known for wielding sickles in their twin tails, and now Greasel has brought that back into style---of course it's not a real sickle that can do any permanent harm, though it definitely hurts! Though it's not a particularly strong weapon, it's quite fast and slices in a wide arc---and, uniquely, its arc depends on which arm it's on. Right slices vertically, left slices horizontally. Your opponent needs to carefully think about this when fighting a Slickle, or else they may misread an attack! The Slickle also has a Wind Attribute, because, y'know, that's kind of a Kamaitachi's thing.
His second default ARM is the Coolclaw, an Ice-Attribute version of Big Bengal's Clawbreakers. They fire off slowly and slam to the ground for the initial hit, and then scrape back to the user (who can move around but can't use that ARM) dealing additional damage if they slash over the opponent. When keeping an eye on Greasel's afterimages and Revv Up, the opponent may find themselves distracted and forget all about that dangerous claw coming right at them from behind!
Finally there's the Orochi, an Electric-Attribute version of the Hydra that fires off three vertical shots---for Greasel, it's a good idea to choose either the vertical/horizontal sickle and your other ARM that compliments it. For example, the vertical Slickle can take care of air enemies while the Coolclaw pressures them on the ground, and the horizontal Slickle can deal with grounded foes while Orochi puts pressure if they try and jump over it.
His stage is "Highway A6A6" (which could be read as "A-mu A-mu" in Japanese I believe), and in this stage you fight atop a moving truck with a steel-caged arena built atop it! The cage limits your movement somewhat and it's one of the smaller stages, and a quick-moving guy like Greasel is dangerous in such confined quarters! As the truck drives through the night various vehicles can be seen driving by advertising various ARMS products, fighters, and such. The driver of the truck happens to be a member of Greasel's gang by the way, Tank. He's a biker tanuki and the gang's resident mechanical expert, and the only person Greasel considers a friend.