Okay, I made some adjustments, some additions and most importantly, I went through all 92 pages to add levels to anything people remembered to mention on! So here is the new and (hopefully) improved list!:

Opponent -> beatable by (combo)
[] and {} and <> and || are level indicators

Aether[11]{12} -> Coral(M)[10], Elf(M){8}
Air[10]{11} -> Air(MBB)[10], Coral(MM){10}
Amathyst[11]{14} -> Diamond(MB){10}, Crusader(BM)[9](MBM)[6]
Angel[14] -> Mistmoth(MB)[7]
Anubis[14]{11} -> Infinity()[9](M), Pearl(){10}, Crusader(BB)
Athletic[12] -> Fairy(BB)[]
Atlas[10]{14}<13> -> Pearl(BM)[10], Coral(B){10}, Scorpion(M), Diamond(M), Crusader(BBM)<10>
Aurora[13] -> Bat()[10], Diamond(MB)

Boo[12]{13} -> Crusader(BB)[10], Life(BM){10}
Bubble[14]{10}<13> -> Coral(B){10}, Illusion(BBM)[8](BBM)<7>

Ceasar[13] -> Fruitful(), Crusader(MB)[9], Fairy(B)[]
Charm[10] -> Justice(M), Fairy()[10]
Chocolate[11]{13} -> Life(MBB){}, Firestorm(MB)[10], Angel(B), Ice Cream(BBM)[10]
Clockwork[13] -> Aether(MMB)[10]
Coral[13] -> Life(MB)[10]
Cosmic[11] -> Cosmic(B)[7], Unicorn(MB), Mask(MBB)[10]
Crusader[11]{13}<14> -> Fire(BB)[10], Coral(M), Mindvolt(MB){10}, Atlantis(B), Crusader(MM)<9>
Cupid[12] -> Firestorm(M)(MMM)[5]

Dark Angel[10] -> Light(BMB)[10]
Dawntree -> Laserlight(M)
Deep[10]{14} -> Firestorm(M)[10], Coral(B){10}
Diamond[10] -> Fairy(M), Aether(B), Trickster(BM)[10]
Dream[14] -> Bat(MBB)[10], Aether(MB)

Eagle[12]{13} -> Crusader(BM)[9](BM){9}
Easter[13]{10}<14> -> Atlandtis(M)[10], Diamond()[10], Crusader(BM)<9>, Zombie(MB){10}
Eclipse[10] -> Crusader(B), Laserlight, Athletic(BMM)[10]
Elf[13]{11}<10> -> Infinity()[9], Crusader(BM){9}, Laserlight(MMM)[10](M)<10>, Athletic(BMB)

Fairy[13] -> Aether(M)(MB), Crusader(BM)[9], Firestorm(B), Mask(MBM)
Familiar[12]{14} -> Life(BM)[10](BM){}
Fire[11]{12} -> Mist(MM)[9], Mindvolt(MM){9}
Fireworks[13]{11}<14> -> Fairy(MBB)[], Honeybee(M){4}(MMM), Mindvolt(M)<9>
Flower[11]{12} -> Crusader(B){9}, Athletic(BMM)[10]
Forest[10]{11} -> Laserlight(M)[10](MBM){3}, Justice(M), Fire(BM){10}
Forestfire[10]{13} -> Storm(M)[9], Mindvolt(BM){9}
Four-Leaf[11]{13} -> Crusader(BM){9}, Pumpkin(BM)[10]
Fruitful[13] -> Elf(MB), Mindvolt()[10]
Fuzzy[11]{14} -> Scarecrow(BM)[10], Crusader(MB){9}

Genie[14]{13} -> Life(MBM){10}, Forestfire(BMB)[10]
Goblin[14] -> Cupid(), Angel(M)[10]
Gold[14]{13} -> Landworm(M){10}, Atlantis(BB)[10]

Hammerhead[14] -> Atlas(M)[6]
Helios[14]{12}<13> -> Coral(M)[10], Firestorm(M){10}, Crusader(M)<9>
Honeybee[11]{14}<10> -> Clockwork(B), Mermaid(BM)[10], Crusader(MB){9}(M)<9>
Hunter[10]{14} -> Wild(B)[10](BM), Rose(MBM), Helios(MM), Bat(){9}
Hypnotic[7] -> Planet(BMM)[10]

Ice Cream[14] -> Landworm(M)[10], Forestfire(M), Diamond()
Illusion[12] -> Crusader(BMM)[9](B)[9], Dream(MMB)
Infinity[10]{11}<14> -> Wizard(M)[10], Crusader(BB), Diamond(MB){10}(BMM)<10>
Island[11] -> Witch(M), Mindvolt(M)[9](MB)

Justice[13] -> Unicorn(BM)[7], Mindvolt(M)[10]

Kite[11] -> Landworm(M)[10], Firestorm(BBB)

Landworm[11] -> Mermaid(B)[10], Crusader(MB)[6]
Laserlight[10] -> Coral(B)[10]
Leftheart[12] -> Mirage(B)(BB)[10], Coral(MBB)
Leopard[11]{13} -> Crusader(M){}, Fire(B)[10]
Leviathan[12]{11}<14> -> Planet(B), Coral(M)[10], Fruitful(M){10}, Clown(MB), Crusader(MB){9}(MMM)[9], Aurora

(BB)<10>
Life[11] -> Eagle(M)[10], Topaz()
Light[12]{10} -> Mercury(BB){10}, Pegasus(B)[6]
Lightning[13] -> Landworm(), Diamond(M)[10]
Lotus[14] -> Ruby()[9]
Love[13]{14}<11> -> Leftheart(M)<10>, Laserlight(BMM)[7], Mistmoth(BMB)[7](BB){7}
Luck[13]{14} -> Diamond(MB){10}(M)[]

Magic[11]{13} -> Diamond(MM)[10], Life(MM){10}, Wild(BB)
Mask[11] -> Fire(MB)[10], Dream(M)[10], Crusader(MB)[]
Medusa[13]{10} -> Crusader(M)[9], Life(BM){}
Mercury[14] -> Diamond(MB)[10], Justice(M)
Mermaid -> Easter()
Mindvolt[10]{14}<11> -> Fruitful(B)(MB){10}, Landworm(B)<10>, Peacock()[4]
Mirage[14] -> Origami(BB), Diamond(B)[10]
Mist[14] -> Origami()[10]
Mistmoth[11]{13} -> Landworm(B)[10], Diamond, Fairy(M){10}()[10]
Mythic[14]{13} -> Angel(M)[10], Fire(BMM){10}

Naga[11]{12}<13> -> Crusader(B)(BM)<9>, Dream()[10], Night(MB){10}, Scorpion(M)
Night[13]{11}<10> -> Passion(MMM){10}, Griffin(BMB)[10], Crusader(MB)<9>(MBM)<9>
Night Elf[12] -> Atlantis(B), Crusader(BB)[9]

Parakeet[14]{11}<12>|10| -> Ice Cream(BB){10}(BBB)||, Mirage(MBM)<10>(M), Fruitful(BMB)[10], Lightning(MM)
Passion[11] -> Life(M), Firework(), Laserlight(MM)[10]
Peacock[10]{12}<13> -> Parakeet(B)[10], Wild(MB){10}, Atlantis(BMM){10}(BMM)<10>, Crusader(MB)<9>
Pearl[13] -> Crusader(B)[9]
Pegasus[13]{12}<14> -> Scorpion(), Crusader(M)[9](BM)<9>, Landworm(M){10}, Laserlight(MM), Firestorm(MM)[10]
Planet[12] -> Crusader(M)[9], Justice (MM)
Poison[12] -> Wild(MBM)[10], Origami(BB)
Pumpkin[10]{13} -> Atlantis(M), Honeybee(B)[10], Justice(M), Diamond(BMM){10}

Quartz -> Honeybee(BB), Familiar(MBB)
Quetzal[12] -> Wild(B), Planet(B), Love, Crusader(B)[10], Diamond(BB)[10]

Rightheart[11]{14} -> Athletic(BB)[10], Mindvolt(MB){9}
Rose[13]{11}<12> -> Sapphire[10], Coral(M){10}, Mist(MM)<9>
Ruby[11]{14} -> Griffin(MB){10}, Scorpion(BB)[10], Helios(BB)

Samurai[14] -> Clown, Goblin(MB)[10]
Sapphire[12]{14} -> Fire(M)[10], Athletic(B), Eagle(B), Landworm(BB){10}
Saturn[11] -> Cosmic(BM)[7], Justice(M)
Scarecrow[13]{10} -> Honeybee(M)[10](BM)[10], Crusader(MM){9}
Scorpion -> Mist(B), Infinity()
Seabreeze -> Scorpion(B)
Serpent[11]{13}<12> -> Landworm(B)[10], Honeybee(MB)[10](BM){10}, Fairy(MBM){10}
Snowman[11]{14}<12> -> Island(B)[10], Life(MB)<10>, Leopard(M){10}
Storm[13]{12}<11> -> Origami(BBM)[10], Air(MB){10}, Fruitful(MB)<10>
Sunset -> Crusader(MB)
Sunrise -> Crusader(MB), Justice(B)
Super[12]{10} -> Leopard(){10}, Serpent()[10]

Tiny[14] -> Honeybee(BM)[]
Titan[14]{10} -> Leopard(BBM)[10], Serpent(BM){10}
Topaz[12]{13} -> Scarecrow(B){10}, Diamond()[10]
Treasure[13]{10} -> Gold, Elf()[7](B), Diamond(M){10}
Trickster[9]{14}<12>|11| -> Parakeet(B){10}, Forestfire(B)<10>, Diamond(M){10}, Crusader(M)|9|, Serpent[10]
Turkey[13]{11} -> Fruitful(MMB)[10], Storm(MMM)[9], Fairy(B){}
Tusker[11] -> Atlantis(M)[10], Planet()[7], Peacock(BM)[7]

Unicorn[13]{12} -> Planet()[10], Wild(M){10}, Crusader(MB)[10]

Virtue[13]{10} -> Aether(), Virtue(M), Honeybee(MB)[], Titan(M), Fire()[10], Night(M){10}

Water[11]{14}<12> -> Firestorm(MB){10}, Fairy(MBM), Life(BM)<10>, Atlantis(B)[10]
Wild[13]{11} -> Parakeet(M)[10], Laserlight(MM)[10], Diamond(MB){10}
Winter[12]{11} -> Fairy(M)[10], Coral(M){10}, Aether(MM)[10]
Witch[14] -> Crusader(BM)[9]
Wizard[12]{14}<13> -> Fruitful(BB)[10], Crusader(BM){9}, Elf(BM)<8>

Zombie[11]{13} -> Eagle()[8], Parakeet(M)[10], Easter(MB), Diamond(MBB){10}

--------

To clarify how it works I want to take out a few examples:

Crusader[11]{13}<14> -> Fire(BB)[10], Coral(M), Mindvolt(MB){10}, Atlantis(B), Crusader(MM)<9>

This one says, that if you are currently battling a Crusader dragon of lvl 11, it has previously been beat by another player by a lvl 10 Fire dragon with a B+B combo(matching the [] brackets), if you are battling a lvl 13 Crusader draon, previously a player has been successful with using a lvl 10 Mindvolt with the M+B combo (by matching the {} brackets) - you get the idea.

If there is ever an empty set of brackets, it is because someone forgot to put down the level/combo he used, but I added them to the list for completion.

Hope it helps!

My ID is on the left, feel free to add me in game if you have any questions or additions you'd like for the lidt