Super Smash Bros. Ultimate players can already choose between tons of playable characters to fight with, but the idea of new characters is always exciting. Now that Sephiroth is in Smash, imaginations have been running wild with other possibilities. There are a few rules for DLC characters that have been put in place in the past, but with each new character it seems that one or more of these rules are broken. Because of this, theoretically anything is possible, even if it seems highly unlikely to ever occur. These are some improbable characters that could be added to Smash but probably never will be.
For those that don't know, there are a couple unspoken rules regarding DLC characters. For a time, players thought that spirits could never be upgraded into full playable characters, but Min-Min proved that assumption wrong. It was also believed that DLC characters would be from unique franchises not yet represented in the game, but the introduction of Byleth once again nullified this rule. One rule that has stood the test of time is that Super Smash Bros. Ultimate characters must originate from video games, this being the main reason that characters like Goku and Superman aren't allowed in the game.
Hades - Zagreus
Zagreus from Supergiant Games' Hades is unlikely for a number of reasons, but the most obvious one is timing. More likely than not, Nintendo already knows who every DLC character in the current Fighters Pass will be, and since all of that was probably determined some time ago, Zagreus doesn't seem likely. Though Hades has been in early access since December 10, 2019, the game really picked up steam at its official release in September of 2020. This alone is more than enough to make Zagreus an unlikely contender for a spot in the second Fighters Pass.
All that said, it's hard to deny that he would be a perfect fit for the game. Between his large arsenal of weapons, various god-given abilities, and agile playstyle, he could easily run with the other characters already in the game. Zagreus' neutral special could grant him boons from certain gods, while his forwards special could be his cast. Up special would likely be his double dash ability, and the down special could a call ability or other special attack. As interesting as it would be to see Zagreus in Smash, fans shouldn't hold their breath for this.
Monster Hunter World: Iceborne - Hunter
There's a surprising amount of representation for the Monster Hunter franchise within Super Smash Bros. Ultimate, with the biggest perhaps being the inclusion of Rathalos as a boss enemy. This iconic monster also appears as an assist trophy within the same title, and the franchise even started to work its way into Smash before this. In Smash 4, players could get two Monster Hunter themed armor sets based on the Hunter's set and the Rathalos set for Mii Swordfighter, but those costumes haven't carried into Smash Ultimate.
Technically speaking, this is a character that checks all the boxes and could be added, but it seems like it would be highly unlikely. The main reason why fans shouldn't expect to see Hunter in Super Smash Bros. Ultimate is that the character would be an extremely difficult fighter to implement in a satisfying way. Players can choose between 14 different types of weapons, countless different armor sets, and a ton of different equipment. Cramming all of this into one character would be nearly impossible, so Nintendo would have to pick and choose what aspects of the character would shine through in the Smash version.
Digimon - WarGreymon (or Agumon)
This may seem like it's coming out of left field, but WarGreymon would be an incredible addition to Super Smash Bros. Ultimate, and actually meets all the unspoken requirements discussed earlier. Though Digimon is best known for the iconic anime, it actually originated as Digital Monster (Virtual Pet), a Tamagotchi like game. What's more, there aren't currently any Digimon representatives in the game, and he certainly isn't a spirit. Naturally, this inclusion is unlikely mostly because Digimon is essentially the direct rival of Pokemon, one of Nintendo's biggest franchises.
In Super Smash Bros. Ultimate, WarGreymon could use an assortment of its already conveniently named attacks as its special moves. Neutral special could allow WarGreymon to harness the energy of his iconic Terra Force attack, while his up special recovery could be Great Tornado. Down special could adapt the move Brave Shield, which could act as a counter for the Digimon, while his final attack, forward special, could easily be Mega Claw or Grey Fire. Not only would he be a powerful fighter, but fans would finally get to see WarGreymon square off against Charizard and other Pokemon. The main reason why this character is would be so interesting to see in Super Smash Bros. Ultimate is also the main reason why he probably will never be added.
Soul Calibur - Nightmare
Super Smash Bros. Ultimate started a trend of including more charaters from other fighting games in its roster. Notable examples of this include Ryu and Ken from Street Fighter and Terry Bogard from SNK, so why not something from the Soul Calibur franchise? As far as fighting games goes, Soul Calibur definitely isn't the most widely recognized, but that doesn't mean that Nightmare wouldn't be a good addition to the ever-expanding roster of Super Smash Bros. Ultimate.
While there are plenty of other characters from the franchise that could fit well in Smash, Nightmare is really the mascot of the franchise and represents a fighting style that isn't present in Smash really. An alternate costume to make him look like Siegfried and wield the Soul Calibur instead of Soul Edge would also be a nice touch, allowing for two characters to be represented in a way. Link from The Legend of Zelda has appeared in Soul Calibur games in the past, so this type of collaboration isn't entirely out of the question.
Super Smash Bros. Ultimate is available now on Nintendo Switch.