This is something I was thinking of doing for fun but i want to see how big we can make the list. I'm looking at rivalries between tribes of monsters and on sub-groups of monsters, such as The Archlords VS The Archfiends, their effects are quite opposite each other ie Archlord Zerato/Mazera DeVille and the good/evil struggle is clear. That's what i'm getting at. I'll start things off with a few i've found and i'll update them when people suggest some more. So have a think and see how many you can find!

Yugioh Monster Group Rivalries

Archlords VS Archfiends
Gravekeepers VS Dark Scorpion Burglars
Dragons VS Spellcasters
Water Monsters VS Fire Monsters
Warriors VS Zombies
Fiends VS Fairys

Individual Monster Rivalries

Marauding Captain VS Gagagigo
Marauding Captain VS Inpachi
Marauding Captain VS Terrorking Archfiend
Freed the Brave Wanderer VS Gagagigo
Harpie Ladie's VS The Ojama's

Interesting concept. Though I notice as yet there have not been any

"Elemental Villans" to go head to head with the E-heros.lol

May I ask how you came up with "Warrior vs Zombie"?

The Warrior/Zombie is the great warrior's VS the Undead. That and look at Ryu Kokki and Getsu Fuhma:

Ryu Kokkie - if a monster that battles with this monster is a Warrior or Spellcaster-Type monster, destroy that monster at the end of the damage step

Getsu Fuhma: if a monster taht battles with this monster is a Fiend or Zombie-Type monster, destroy that monster at the end of the damage step.

Both tribes can automatically destroy the other which leads to rivalry. That's how i looked at it i guess, Meh i'm open to cruiticism, Like the idea of 'Elemental Villans' though!!!!

Ahhh, I seeee now.

As for the "E-Villans"
Every Hero needs Villan to fight, So where are they?

BTW,

You may wish to add

Faries vs Fiends and I dont refer to the Archlords/Fiends

and (Possibly, not quite sure on this one)

Warrior vs Dragon

I think it should be beasts VS Spellcasters.

I'm interested to know why you think that should be the case, since i drew the Dragon/Spellcaster rivalry from the Blue-Eyes/Dark Magician rivalry seen in the anime and the power that the Dark Paladin has in the TCG.

And Dragonslayer, i can't say i agree with the warrior/Dragon rivalry. True Buster Blader kick's dragon's hide but there is also 'Dragonic Attack' and Kaibaman - all warriors in support of Dragons. We'll see what others think

this isnt a type rivalry but a rivalry between 2 cards is gagagigo vs marauding captain.

I think that one counts sharingan, i hadn't thought about thoes two, considering theres about half-a-dozen cards representing their history. Good call.

there are also some teams like D.D. warrior lady, manticore of darkness, D.D. warrior on dimension fusion, return from different dimension and i think another card.

more battles:
terror king archfiend vs marauding captain on battle sacared and staunce defender(i think) (man marauding captain likes to fight everyone)
ojamas vs harpies on harpies hunting ground and i think one other card.

Good finds Sharingan, I'll have to go hunting some more. List updated (and starting to look promising i might add ).

warrior vs. spellcaster
dragon vs. beast

beast vs everything, grrrrrrrrr!!!! im mad stay back, grrrrrrrr!!!