Yes, this is getting it's own page since there's going to be so many.
(Feel free to add any you think off too)
And no, they don't have to be in the game to be used.
But I'll take adding them here as you wanting them in the game.
(Just note that this is broken into 3 categories depending on how many characters are involved)
Tag Team Fatalities
Star and Yomaz- Thicker Than Water (Star creates a black hole on 1 side of the opponent and Yomaz creates a wormhole on the other side of the opponent and the gravity rips their opponent in half)
Nick and Lunari- Nickolari (Nick and Lunari fuse into Nickolari and desintegrate the opponent)
Ty and TLK- The Lich-Copter (Ty begin to spin his sword around like a helicopter blade and TLK uses telekinesis to move the opponent into the blade, chopping them into pieces)
Ion and Corta- Guardian-Sized Smackdown (Ion blasts the opponent and Corta calls the rest of the team. Then they all take turns beating the shit out of the opponent before Ion snaps their neck)
Rudy and Squall- 21 Guns (Rudy and Squall at first look like they're about to duel. Then they both turn their guns/bow to the opponent and begin shooting rounds/arrows into them. Just like the title, they shoot the opponent a total of 21 times)
Axel and Zegram- Harvestors Of Souls (Axel and Zegram both grab the opponent and begin punching the hell out of him/her. Then they rip the opponent in half and Axel pulls their soul out. Then Zegram takes the soul and sends it to Hell)
Io and Axel- Soulnado (Io summons the rest of the magic spirits, and Axel creates a tornado that lifts the opponent into the air before all of the spirits fly around with the tornado, increasing it's speed so drastically, the opponent is ripped to shreds)
Rudy and Angel- A Shot In The Dark
Eden and Mia- Mother Earth's Core
Nick and TLK- Like Father, Like Son
Vanguard and Gabranth- ???
Dillian and Dalton- Earth-Shaking Jutsu
Joanna and Ricky- Daddy's Girl
Rudy and Xia- Bullseye
Rudy and Otega- Masters Of Blasters
Cydik and Metal- Mettalic Purge
Nick and Dawn- ???
Dillian and Rosa- ???
Ashura and Jessica- Shuriken Storm
Nick and Xirsec- Brotherhood
Ion and Johnny- Radiation Poisoning (Johnny throws 100 small Poisonous Needles at his foe then Ion Blasts his foe with a Atomic Bolt right through the chest, in which Poisoned Blood is spewing out of him/her chest, Johnny then rips his/her head off)
Nick and Squall- Bahamut's Tear
Angel and Legna- Burn In My Light
Angel and Zezko- Hell's Judgement
Rosa and Cydik- Technomancery (Cydik pulls out Techno enhancers fro his backpack as Rosa blasts the opponent relentlessly with cyber energy. Then Cydik uses the enhancers to power Rosa's cyberkinesis up to the point where she blasts a laser of cyber energy that decimates the opponent)
Exo and Metal- Death Machine
Nate and Mikasa- Lifted Spirits
Io and Lexie- ???
Xia and Johnny 1- Eternal Rest
Xia and Johnny 2- Hands of God
Nick and Justin- Student and Teacher
Nick and Vuxo- Alpha and Omega
Lunari and Io- Spirit Synergy (Lunari rips the opponent's spirit from their body, and passes it to Io, who corrodes it with her magic.)
Xena and Haely- Bloodletters (Haely bites the opponent's neck, and then kicks them in the back sending them flying over to Xena, who impales them with her claws before blasting their heart out of their chest. Xena then proceeds to walk over and pick up the heart, she pops it and stuffs it inside of the opponent's mouth as Haely then uses a gust of wind to knock their body over before they both walk away)
Zezko and Pyro- Hellfire Coffin
Angel and Joanna- ???
Alaine and Zigath- Outta This World (Alaine holds a psychic blade over her head, and jumps into Zigath's hands. He holds her by the legs while winding up a throw, sending Alaine and her blade right through the opponent's chest)
Nathanyl and Haely- ???
Nathanyl and Cole- Treehouse of Terror
Arc and Liquid- Plasma Displacer
Squall and Rikai- ???
Ashura and Metal- Full Metal Burst
Ty and Ashura- ???
Ashura and Glitrix- ???
Squall and Aden- ???
Phantom and Gabranth- Darkness Incarnate (Phantom gathers all the dark energy from around him, before joining with Gabranth, who pulls the opponent into a portal. After a brief moment of silence, the portal re-opens with Gabranth jumping out, followed by Phantom, and then a torrent of blood)
Lunari and Squall- Altered Spirits (Lunari uses her spirit form, joining with Squall, who slashes straight through the opponent before sheathing his blade. Then as Lunari leaves Squall's body, the opponent explodes into pieces)
Vuxo and Legna- God and Angel
Nick, Lunari and Dillian- Flaming Spiritual Ninja
Nick, Xirsec, and TLK- Family Bonding
Axel, Zegram and Monoza- Reaping Benefits
Joanna, Ricky, and Zezko- Unholy Trinity
Dillian, Sarah, and Dalton- Fire Pit
Belial, Phantom, and Gabranth- ???
Ashura, Alexxa, and Ted- ???
Ty, Squall, and Aden- ???
Lexie, Sarah, and Alaine- Pint-Sized Pain
Vuxo, Legna, and Maximus-
(Note:these are 4-man fatalities)
Nick, Lunari, Dillian, and Rosa- Fellow Students
Lunari, Rosa, Io, and Lexie- Girl's Night Out (All four nod to each other. Lexie pops the opponent's eardrums, Rosa drives a cyber blade through their chest, Io fires a magic blast at their head, and Lunari rips their spirit apart. )
Axel, Zegram, Lexias, and Monoza- ???