Yes, another OTK as this is my favourite type of deck.

This deck relies on the use of three main cards: Evil Hero Dark Gaia, Dark Fusion, Evil Hero Infernal Gainer.

1. Activate Dark Fusion and fuse Big Piece Golem (2100 ATK) and Evil Hero Malicious Edge (2600 ATK) to summon Evil Hero Dark Gaia (4700 ATK).
   
2. Summon Evil Hero Infernal Gainer and activate Megamorph. (9400 ATK, if attack twice = 18800 ATK).Note that u can still win if u don't use megamorph, just gotta have a clear shot for direct attack.
   
3. Use Evil Hero Infernal Gainer's effect on Evil Hero Dark Gaia : You can use Evil Hero Infernal Gainer's effect the turn you use Dark Fusion, because Dark Fusion's effect specified that your monster cannot be targeted as a target by your opponent's card effect.
   
4. Attack twice with Evil Hero Dark Gaia and use his effect if attacking an enemy monster.
   
5. You can also use Dark Calling on the same turn to summon another Evil Hero Dark Gaia, having the same amount of attack points, but is vulnerable to your opponent's effects.
   

Some Notes:
You can get Evil Hero Dark Gaia's attack up to 7500 if you're using cards like The Wicked Dreadroot, Darkness Neosphere or Raviel, Lord of Phantasms and Valkyrion the Magna Warrior, or Gaia Plate the Earth Giant. With two of these attacks, you have 7000 damage left over.
Dark Fusion makes Evil Hero Dark Gaia immune to a lot of traps and spells for the turn he is summoned. However, he is still vulnerable to non-targeting effects like Torrential Tribute and Mirror Force.


For Deck Construction, I recommend the usage of Monarchs, as they are high lvl and have both earth and fiend property.Gorz and Earth Giant are another good example.Be sure to have spells like Trade-In,Allure of Darkness,Monster Gate just in case you end up with a crappy hand.Pot of Avarice is a nice save meh plox card too.As I said earlier Dark Fusion and Dark Calling are a must.
For Traps get something that leaves opponent open like Trap Stun,Royal Decree and etc.In case you don't better get some spells that do the job, cuz you will need em.Ojama Trio is an excellent example for quick OTK if you don't want to take any chances.

Lefover Notes:You could include tuners too, as a deck like this can easily be used for Synchro Summon.Fiend Roar Deity Raven is the card you need for that.You are open to another choice ofcourse, that is just what I preffer to use in this deck.