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.
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