(*My Preferred)
Ultimate Ignitorch - Krakatoa/Magmarok
https://www.deviantart.com/supertodd9/art/Ultimate-Heatblast-579597859
Extra Power: Arms and legs melt into magma that can be stretched, molded, and re-hardened for varying uses. Loses flight capabilities.
U Smackdown (Musculomand) - *Ares/Kratos
https://www.deviantart.com/zigwolf/art/Ultimate-Four-Arms-532257802
U Geminus (Strechson) - Supernumerarian/Supernumerary
https://www.deviantart.com/mrmustart/art/Ultimate-Alien-20-Ditto-882246545
Extra Power: Black Sperm from One Punch Man could buff up his arm using his other cells. Imagine that, but to a lesser degree. Can stretch like Mr Fantastic. Multiply limbs. Tradeoff is he can't clone himself.
U Adam Antium (Taydensapien) - Kullinan
https://www.deviantart.com/insane-mane/art/Ultimate-Diamondhead-Request-for-Aaron1248-647820141
Power Trade-Off - Crystallizes anything he touches, but can no longer shoot them out. He can still reshape himself, though.
U Arctiguana [Subzero Manzardill] - Iceberguana/*Ice Age
https://www.deviantart.com/insane-mane/art/OV-Ultimate-Arctiguana-816239872
U Terrorwatt - Petawhatt
https://www.deviantart.com/mrmustart/art/Ultimate-Alien-14-Buzzshock-880114471
Power Tradeoff - Rather than split into copies, Petawhatt grows in size and power with more electricity. At his strongest, he is pure energy.
U Tenwolf [Timber Loboan] - Direwolf/Hundberus
https://www.deviantart.com/minx4321/art/Ben-10-Albedo-Aliens-Ultimate-Loboan-890110655
U Dragonfunk - Funk Tank
U Borborygmus (Gluttomand) - Borborumbler
https://www.deviantart.com/wilann/art/Ultimate-Upchuck-Ben-10-fanart-882141817
U Insanine [Typhlalopex Locutor] - Apexanine (Apex + Canine)
U Argus - Pirseev
(Perceive)
https://www.deviantart.com/insane-mane/art/Ultimate-Eye-Guy-630173025
U Cycrops - Phero-Crops
https://www.deviantart.com/mrmustart/art/Ultimate-Alien-12-Wildvine-879507034
U Masiv [To'kunova] - Supramasiv
https://www.deviantart.com/insane-mane/art/OV-Ultimate-Way-Big-817879101
OR
https://www.deviantart.com/leonellnoll/art/Ultimate-Way-Big-Fan-Art-Commission-883275844
U Brawntosaurus[Vaxamissilian] - Gatlisaur/Ballistasaur
/Gatling Gun/
https://www.deviantart.com/insane-mane/art/OV-Ultimate-Humungousaur-814791006
U Volcamoss [Kerosonian] - Killosene/*Plasmarsh/Mirewood
/Kerosene; Plasma + Marsh/
Bloomed Ultimate: https://www.deviantart.com/insane-mane/art/OV-Ultimate-Swampfire-813573059
U Cacophony [Volumoid] - Megahertz/Beat Boss
https://www.deviantart.com/noahsalmon/art/Ultimate-Echo-Echo-Redesigns-873158512
U Simirachnid [Gorantula/Tarzantula] - *Arachnorilla/Taranturilla
U Intellectionary - EIDOC (Evolved Intelligence Designed Only for Combat)
https://www.deviantart.com/insane-mane/art/OV-Ultimate-Grey-Matter-813686170
Ultimate Prismore (Sugilisapien) : Prismorite
https://www.deviantart.com/ultimatrix10/art/Ultimate-Chromastone-version-2-509634847
OR
https://www.deviantart.com/xzorshio/art/Concept-Art-Ultimate-Chromastone-681681228
U Somnifae - Oberon/Morpheus (Oberphius?)
https://www.deviantart.com/artman196/art/Ultimate-Pesky-Dust-807111185
U Serial Chiller [Calidofriggian] - Frostburnoth
/Frostburn, Burn off, Moth/
U Brainstorm [Gaussriphlocrustacean cuprimace] - Railstorm
5YL Ultimate Brainstorm (Copper Cannon)
U Planetoid (Schwarzsteroid) - *Systemoid/Pallas
/Planetary System; One of the largest asteroids in the solar system./
https://www.deviantart.com/insane-mane/art/OV-Ultimate-Gravattack-815291413
U Pterosoar - Pterosonic
https://www.deviantart.com/insane-mane/art/Ultimate-Astrodactyl-Request-649219157
U Aggro [Vinoffian] - Graven
U Ricoshell [Arburian Acerrota]- Ricosteel
https://www.deviantart.com/insane-mane/art/OV-Ultimate-Cannonbolt-819682097
U Jet Ray (Astrophibian/Astracean) - Lumina Ray
5YL Ultimate Jet Ray
U Whipskers (Monstaxian) - MonsTash
https://www.deviantart.com/xxcodex47xx/art/Ultimate-Mole-Stache-878008047
U Ball Weevil - Boom Weevil
https://www.deviantart.com/rzgmon200/art/Into-the-Omniverse-Ultimate-Ball-Weevil-820196064
U Impolition [Archaküle] - Arch Impolition
/Arch Imp + Demolition/
https://www.deviantart.com/insane-mane/art/Ultimate-Jury-Rigg-629467794
U Kabito - Kablasto
https://www.deviantart.com/artman196/art/ULTIMATE-EATLE-776835043
U Mummifight - Sarcophagrief
https://www.deviantart.com/darkslagg2/art/Ultimate-Snare-Oh-879929351
U Adonis (Nortrebian) - Ultragius
/Ultrageous; Looks like a mix of Ultimos and DC's Doomsday/
U Draconem - Bahamut
U Snapclaw - Paralith
U Polyhedron - Polychoron/Orthoplex/Hypercube
U Nosmirc - Vermilion/ *Imperial Red
U Eriphas - Ultramarine/ *Imperial Blue
//Fusion Ultimate Letoiv - Tyrian Purple//
U Hellion [Muspelphage] - Arch Hellion
U Threepointonefour - Prime Number
U Mechrobe - Commandrone
https://www.deviantart.com/cat-in-rogue/art/Ultimate-Nanomech-826429499
U Ek'toc'sm [Erebonurian] - Hades
FORM UNKNOWN. VISUAL AND TECHNOLOGICAL ATTEMPTS TO PERCEIVE FORM HAVE FAILED.
U Joltozoa - Jolt-o-War
https://www.deviantart.com/cat-in-rogue/art/Ultimate-AmpFibian-798954525
U Pretorishock - Pretorsenal
https://www.deviantart.com/artman196/art/ULTIMATE-FRANKENSTRIKE-777012874
U Alu KO - Alukill
https://www.deviantart.com/artman196/art/ULTIMATE-WHAMPIRE-780278288
https://www.deviantart.com/jupago25/art/Ultimate-Whampire-889322771
U Biteforce - Dunkleo-Force/Kingfish
https://www.deviantart.com/nickfries55/art/ULTIMATE-Ripjaws-869462420
U Chemix (Factulence) - Chemtory
https://www.deviantart.com/cat-in-rogue/art/Ultimate-Gutrot-811465086
U MY-LZ - FSTST
https://www.deviantart.com/kamran10000/art/Ultimate-Xlr8-Ben-10000-499025894
U Anadromus (Nessyperambuloid) - Serpendromus
https://www.deviantart.com/spyro2108/art/Ben-10-Alien-U-Walkatrout-851174599
U Richter - Richtavator/Tankavator
https://www.deviantart.com/wilann/art/Ben-10-Ultimate-Armodrillo-fanart-832998459
U Mod - Override/Admin
https://www.deviantart.com/insane-mane/art/Ultimate-Upgrade-629765620
Extra Power: Wireless Control - Can control entire fleets without merging, but must merge to upgrade.
U Insidius (Noxomination) - Insidiphobia
https://www.deviantart.com/rzgmon200/art/Into-the-Omniverse-Ultimate-Toepick-882070190
https://www.deviantart.com/lucaschannel07/art/Ultimate-Omniverse-Ultimate-Toepick-894020468
U Zig Foot (Rajangopithecus) - Ooshocku
https://www.deviantart.com/misakalovesyou/art/Ultimate-Shocksquatch-and-Ultimate-Astrodactyl-888751759
U Brixx - Lava Brixx
https://www.deviantart.com/xxcodex47xx/art/Ultimate-Bloxx-Albedo-Version-879300962
U Pada Grodah (Incursean aposema) - Cain Todah
https://www.deviantart.com/artman196/art/ULTIMATE-BULLFRAG-776836736
Extra Power: Sharp bone claws stick out of his fingertips.
U Svedberg (Chronosurgien) - Svedbuster
https://www.reddit.com/r/Ben10/comments/lw4oq8/my_ultimate_clockwork_design/
(TIME RAY CANNONS!)
U Korosiv - Korosmash
5YL Ultimate Goop
Extra Power: Can control the viscosity, acidity, and adhesiveness of his slime.
U Magnitoid - Polarian
https://www.deviantart.com/wilann/art/Ben-10-Ultimate-Lodestar-900526821
U Kickit - Clash Hopper
https://www.deviantart.com/xxcodex47xx/art/Ultimate-Crashhopper-878598103
U Churnobyl (Prypianobyl-B) - Cherno-Thrill
https://www.deviantart.com/creaturemasterprods/art/Ultimate-NRG-702143931
U Hydrollusk (Blastrishan) - Bunkrollusk
https://www.deviantart.com/misakalovesyou/art/Ultimate-Water-Hazard-908492447
U Aeolus (Geochelone Ventus) - Aeol Shots
https://www.deviantart.com/nickfries55/art/Ultimate-Terraspin-Transparent-909075346
U Ophidion (Naganectian) - Ophidaconda
//Eunectes//
U Quillshot - Rat Plastard
U Allotrope - Deus Ex Genetica
U Kikaxx (Cthuvaxian) - Killax
https://www.deviantart.com/minx4321/art/Ben-10-Albedo-Aliens-Ult-Chimera-Sui-Generis-899844291
U Kakusenshi - Kakubomu
https://www.deviantart.com/insane-mane/art/Ultimate-Atomix-631570341
Extra Power: Can absorb surrounding radiation and convert it, i.e., making plutonium harmless.
U Nekoila - Overcharge
U Shock Ore (Fulmaxi) - Overvolt
https://www.deviantart.com/minx4321/art/Ben-10-Albedo-Aliens-Ultimate-Fulmini-904766850
U Chronian [Divinian] - Eternity
https://www.deviantart.com/minx4321/art/Ben-10-Albedo-Aliens-Ultimate-Chronian-901166370
U Anodite - Mana-iac
5yl Ultimate Anodite
U Entity (Beyondsapien) -> Over-Entity
https://www.deviantart.com/leonellnoll/art/Ultimate-Alien-X-World-Destroyer-Commission-885189438
//The power difference between a Celestialsapien and an Ultimate Celestialsapien is the same difference between a Human and a Celestialsapien.//