These are the bosses that appear in either Classic Mode or Story Mode. The Main Boss that appear in both is Minion.
Main Boss (Main Antagonist)[]
Minion (Twisted Metal) and is known as Satan himself
Other Bosses (Secret Bosses)[]
Biollante (Godzilla vs Biollante)
Ultron (Avenger: Age of Ultron)
SlaughterDemon (DOOM/WoW: Lich King)
Final War (M.U.G.E.N/Patchmon)
Story Mode Bosses[]
These are not in any kind of order. Just to yet you know.
Senator Armstrong (Metal Gear Rising)
Perfect Chaos (Sonic Adventure)
Obsidius (Godzilla)
Alduin (Elder Scroll V: Skyrim)
Demon Sunset Shimmer (My Little Pony: Equestian Girls)
Corrupted Shinnok (Mortal Kombat X)
Cyberdemon (DOOM 2)
Fleshpound (Killing Floor 2)
Undergrowth (Danny Phantom)
Zombie King Kong (Escape from Bug Island)
Trash Monster (LittleBigPlanet Karting)
Moo (Monster Rancher)
Night Terror (Soul Calibur 3)
Master of Games (Teen Titans)
Seth Rollins (WWE)
Donkey Kong (Pixels)
Krylock Demon (American Dragon Jake Long)
Enemies[]
Much like normal story and Smash Run, These are the random bad guys you'll encounter.
Luchadores (Saints Row the Third)
Microbots (Big Hero 6)
Ghost (Panty & Stocking with Garterbelt)
Jesse Army (M.U.G.E.N)
Ultron Older Suits (Avenger: Age of Ultron)
Gordanians (Teen Titans)
Robotnik's Robots (Sonic the Hedgehog)
Ronins (Saints Row II)
Beedrill (Pokemon)
Ghost Zone Police Department (Danny Phantom)
Oicronians (Futurama)
Tarkatans (Mortal Kombat)
Titans (Attack on Titans)
Creeper (Minecraft)
Shan-Yu Clan (Mulan)
Ghosts (Mystery Skulls: Ghost)
Gremloblin (Gravity Falls)
Lizardman (Soul Calibur)
Joker (Monster Ranchers)
Oni (Mortal Kombat)
Magnetic Enemies (Metal Gear Rising)
Monkeys (Ape Escape)
Imp (DOOM 2)
Cacodemons (DOOM 2)
Anti-Fairys (Fairly OddParents)
Birdo (Super Mario Bros 2)
Roger Aliens (American Dad)
Bot (Zelda 2: Adventure of Link)
Digdogger (Zelda 2: Adventure of Link)
Robot Swat (The LEGO Movie)
Bandits (Elder Scroll V: Skyrim)
Talon (Twisted Metal)
The Hoard (LittleBigPlanet Karting)
Centipede (Pixels)