First of my deck, so far this deck has both been in and won more matches than anyone else. It relies on sending monsters to the grave to pump out its KOSS with overwhelming attack points and using cards such as Lady in Wight or Royal decree for protection. It's weakness lies in banished cards and monster effects. It is rather consistent and if no protection is need KOSS can be given powerful equip card to end the duel quickly

Red-eyes deck, this deck relies on using set-up cards such as Black Stone of legend to summon big monsters from the deck or discards to get Red-eyes in the grave for several methods of special summing. The rate at which these monsters can appear may be overwhleming in addition to the fact that they wield several powerful burn effects, notably Flare Metal Dragon
This 2800 ATK beatstick can summon more Red-eyes and can't be destroyed by card effects for the most part in addition to a hefty sum of 500LP every time an opponents effect is activated. This deck can be used for formidable high level synchro and XYZ summoning

Ryu's deck, not enough information acquired for accurate analysis. This deck seems to rely on banishing a large amount of cards then drawing cards from the banished zone. It also uses mana counters, XYZ, and Phase shift summoning.

Scar's deck(Alexander).This deck is focused on getting spell counters onto the field spell Magical citidal, then summoing Arcanite Magician switching to assault mode to avoid destruction, in order to destroy the opponents field. To do this often a level 5 is special summoned, via effect like The Tricky, and Instant fusion, and synched with Arcane Apprentice to optain a copy of Assault mode ACtivate

 Scar's deck(Megumi) This deck is a destiny hero deck that seems to focus on getting out Destiny Hero- Plasma to negate monsters effects, Horus lvl 8 to negate spells , and most likely a royal decree to negate traps making the opponent powerless.

First my deck, powerful counter cards include banishing or otherwise removing card from my grave. Monster of note, Nanobreaker, possibly the easiest to use counter

Eklispe: Second Red-eyes, There are several powerful anti dragon cards such as. Dragon Capture Jar. and Galaxy Dragon. While buster blader can be used keep in mind the two tribues which can be troublesome

Ryu's deck. While information is limited keep in mind Spell counter cards, anti spell cards, and last day of the witch to beat this deck Also Imperial Iron Wall may be effective here

 Scar's Deck(Alexander). As this deck relies on Arcanite Magician an effective, if temporary stop is Discord. Last Day of the witch is also effective. Skill Drain can be helpful if you have over 2400 atk, or 2900 if in assault mode. Anti spell fragance can slow this deck down as well. Idealy Spell Canceler can be summoned and then protected in a variety of ways, Alternitively Horus lvl 8 can serve this function as well.

 Scar's deck(Megumi). This is a complete lock down deck. Stopping any of the compents is welcome. Given current knowledge Megumi can't stop effects that trigger in the grave, therefor fire and ice hand can be helpful for clearing the field. Other than that the full set up is very hard to beat, disrupting it with anti summon cards and quick decks work well. I have very little for suggestions when fighting this deck except for speed.