I'm a long time Yu-Gi-Oh fan, and I wanna know, what is the Yu-Gi-Oh monster card that has the highest level (currently). Basically, I mean the highest amount of stars on the top of the card.
Basically in the Yu-Gi-Oh anime, each monster card has a level number (the amount of stars at the top of the card), and I want to know which monster card has the highest level.
Example:
An alternate answer to Senshin's answer is however the Fortune Ladies used by Carly Carmine while she was a Dark Signer in the Yu-Gi-Oh! 5D's series. and unlike her Fortune Fairies she used before becoming a Dark Signer the Fortune Ladies are also official cards
while the starting level of the Fortune Ladies is initially low, the highest being 6, their special ability allows them to gain a level every turn which in turn affects their ATK and DEF.
so Fortune Lady Earth which has the highest initial Level of 6 needs only 6 turns to reach Level 12 which is indicated to be the max their special ability will allow them to go up.
Also Fortune Lady Earth and Fortune Lady Dark have the higher multiple for their ATK and DEF out of the Fortune Ladies being 400 which means 400 x 12 = 4800 ATK and DEF which beats all 12 Star Monsters except 3 who's ATK and/or DEF is 5000 but this can be supplemented with spells and traps. with their much lower tribute cost they are quicker to summon especially Earth who's initial 2400 ATK/DEF is close to the 7 star Dark Magician's who requires 2 tributes instead of Earth's single tribute.
their natural flaw is however the fact that they take some time to get powerful unless you use other cards to boost their level. also their special ability stop at Level 12 which means getting them to Level 12 quicker via other cards wont give them as high of a level as if one waited and used the cards afterwards
In the OCG and TCG, monsters cannot have a Level lower than 1, but card effects can freely raise a monster's Level to arbitrarily large values in excess of 12.
Source: Level
depending on how one plays this wait can be problematic. some strategies which could work is to prevent summoning and use Swords of Revealing Light to stop attacks for 3 turns each until a Fortune Lady has enough ATK/DEF to shrug off most attacks
Remember that Kaiba vs. Yugi duel way back in Duelist Kingdom (episodes 22-24) where Yugi polymerized his Mammoth Graveyard with Kaiba's Blue-Eyes Ultimate Dragon? (lol)
Blue-Eyes Ultimate Dragon is a level-12 monster. I don't believe there are any monsters of level 13 or higher. So, there's that. (There are probably other level-12 monsters in the anime, too; a fair number of the monsters on this list seem to show up at one time or another.)
I don't remember seeing any specific instance of monsters having an original level higher than 12 in the anime, and I'm not sure for a particular instance of a highest shown level however:
Some monsters have a ??? or ? level. Sometimes this is because the original level was never revealed; other times it has an effect that derives level from gamestate like some real-world cards do with ATK and DEF (but never level). Some may be implied to be inherently infinite. Super Fusion God has a level of ??? and is a fusion of one monster of each level 1 to 12.
There are some level 0 monsters in 5D's (and, funnily enough, these exist in real cards too!) thanks to the Synchro and Negative/Dark Synchro mechanics.
In ZEXAL, Xyz monsters are introduced, which have ranks rather than levels. They are quite comparable. "New Order 13: Etheric Amon" and "Number iC1000: Numeronius Numeronia" are rank 13. Like the above point, there are also rank 0 cards.
With card effects, any card can have an arbitrarily high level. With looping, any level can be achieved. Level changing is an important mechanic is 5D's, ZEXAL and Arc-V for the Synchro and Xyz mechanics. Some cards like the "F.A. Archetype", "Fortune Lady", and "Dark Strike Fighter" have effects based on levels. With a small number of cards, a ridiculously high novel level can be achieved using level lifter on two monsters of the same type with less than 1000 ATK/DEF, discarding a high-level monster (at best, level 12 like "Yubel the Ultimate Nightmare" for example) thus making them both level 12. Then use "Tannhauser Gate", making both monsters' levels the sum of them: after one use we now have 2 level 24 monsters. Using a second "Tannhauser Gate" gets then up to 48 and a third gets them to 96. For now, we will ignore loops which might make it semi-redundant. Supposing you have "Dark Strike Fighter" and two suitable monsters (same level, >1000 ATK/DEF), use 2 copies of "Tannhauser Gate" and you will be able to drop an opponent from 8000 (or up to 9600) life points to 0 with one use "Dark Strike Fighter"'s effect!
I believe it's this- supreme king dragon black zarc. Only level 13 I've ever seen. 
