Well, that is a hard one. I'd say the zombie world one NOT ZOMBIE MADNESS, because it is very flexable and easy to improve, it is also a powerful deck and it has many powerful cards in it, such as shrink and imperial iron wall.
get dragons collide structure deck first, then epic dawn booster box. makes a perfect deck
either Dinosaurs rage structure deck or Machine revolt structure deck
I reckon that the best structure deck is Dragunity Legion has it has a number of amazing combos that can get the best card in the deck out countless times and it is a good all rounder and it is a good dragon and winged beast deck
I dont know abut best deck possible, but The Dragons Collide Structure deck with some additions is by far the best for speed and power I have used myself..... personally Inzektors are the new trend in speed and power these days though, anyway good luck and good dueling :D
In my opinion, the best Structure Deck is Dragons Roar. It is a simple deck, based on the Red-Eyes Darkness Dragon with Armed Dragon support and a few smart spell and trap cards thrown in. Very easy to tailor it to your own style, and being a Dragon deck (dragons seem to be quite popular) it is easy to find the cards that suit your deck from the couple hundred of dragon cards that are out there. I started with this deck, it taught me about strategy, and how to win with effects, rather than just winning by superbly high attack.The best deck is the Surge of Light deck. When Neo-parsah is summoned, with the help of the field card "Santuary of Light", it can do damage differences between its attack and the defense of the opponent's monster. Not only that it can raise its attack by the difference of the life points of the players. Other monsters in the deck have high attack power and pretty good effects, despite their low levels.
cyber draons and chimeratech fortress dragons
you can have any card in any deck, personnally feinds and dragons and warriors are really really good
There are lots Of Dragons But I Suggest The best fusion Ones are Blue eyes Ultimate dragon Cyber End Dragon And Five headed Dragon It Depends how it fits your deck
The Rise of the Dragon Lord structure deck would be best (and so far the only) choice.
No, there has never been a fiend-specific structure deck. but there has been a structure deck that has mostly fiends
in my opinion Zombie World
the dragunity deck is a structure deck