A Beatdown Deck is a strong offensive Deck which concentrates on using high ATK-powered monsters to bring down the opponent's Life Points as quickly as possible. To have a successful Deck, players must be able to apply pressure to their opponent at the outset of the game before any real strategies can be employed. A common misstep in such a deck is to use powerful monsters simply for their power. A successful deck will include monsters that are not only powerful but have powerful effects to ensure the safety of your monsters.
Very few safety cards should be included in Beatdown Decks. While a select few, such as "Magic Cylinder", may be used, Spell and Trap Cards should focus on clearing the opponent's field as quickly as possible (such as with "Mirror Force", "Torrential Tribute", and other staples) in order to provide for the full potential of the monsters. Monsters should also be Summoned to the Field as quickly as possible. A further possibility is to use Trap Monsters such as "Metal Reflect Slime". Trap Monsters help you to swarm the field quickly, and can be used as tribute fodder. Cards that have a low Level but a high ATK also fit in well.
The most effective ATK stats for Beatdown Decks depend on the metagame, but generally are 1800 or higher for Level 4 or lower monsters, 2400 or higher for Level 5 and 6 monsters, and 2800 or higher for Level 7 or higher monsters.
Cards such as "Blue-Eyes White Dragon" and other powerful Normal Monsters should be left out as they contribute little to the overall function of the Deck. They should only be included if your Deck is a Normal Monster Beatdown Deck, or based around one card, for example "Blue-Eyes White Dragon".
Any monster that requires more than one Tribute should try to be avoided unless they have a game-breaking effect (such as "Beast King Barbaros", who can be either a powerful 3000 ATK beatstick, clear the opponent's field, or be Summoned as a quick 1900 ATK beatstick).
Generally, don't expect most of your monsters staying on the field for more than a few turns. Be aggressive and attack whenever possible. If you draw "Goblin Attack Force" before "Skill Drain", attack with "Goblin" and let it be destroyed when it switches to Defense Position. Waiting a turn or two to get "Drain" might cost you a precious window of opportunity to your opponent's Life Points.
Cards that can target multiple cards for an attack such as "Chaos Ancient Gear Giant" are fantastic against decks based on swarming the field. The aformentioned card also has a very high attack and piercing damage, making it an overall amazing card for beatdown in general and OTKs.
"Evil HERO Malicious Edge" is a wonderful Level 7 monster to include due to his effect that it can be tribute summoned with one tribute when your opponent has a monster on his side of the field. It also inflicts piercing damage and can be searched with "Elemental HERO Stratos". Another powerful card that also has a powerful effect is "Super Conductor Tyranno", due to his high 3300 ATK and the ability to decrease your opponent's life points by tributing a monster on your side of the field. Another really good card is "Black Tyranno" because this card has the ability to pressure your opponent by threatening to punish him or her if he or she goes on the defensive (in which case, they should because you have a 2600 attacker on the field).
A great choice for a beatdown deck would be "Injection Fairy Lily". Its effect of gaining 3,000 attack when attacking or attacked makes a death-machine against most monsters. Be sure to have cards that increase your Life Points, like "Solemn Wishes", so you don't wear out your Life Points too quickly. (**although, do consider that solemn wishes might not be as offensive in a beat-down deck)
Along side fast summoning, putting one "Gigantes" in your deck is usually very effective. A majority of the very good beat down Monsters out there are EARTH-attribute. (ie: "Berserk Gorilla", "Goblin Attack Force" (or any variation thereof), "Chainsaw Insect", "Black Tyranno", etc...) so chances are quite high for you to have at least one EARTH Monster in your Graveyard upon Special Summoning this Monster.
Impressive Level 4 monsters like "Gene-Warped Warwolf", "Slate Warrior", "Berserk Gorilla", "Ape Fighter" and any other cards with around 1900 or more ATK. "Spear Dragon" is usually one of the best bets since it has the decent 1900 attack power AND the capability of damaging your opponent if he or she happens to have a defensive position monster on the field. The downside is that it cannot attack for two turns and remains vulnerable due to it's low defense score.
"Interplanetarypurplythorny Dragon" is usually effective in a Beatdown Deck as it has 2200 ATK and can be Special Summoned as soon as one of your monsters is destroyed and sent to the Graveyard by battle or effect.
Cards that increase their power with certain effects like "Great Maju Garzett", which doubles the attack of the monster Tributed for its Summon, give you access to a greater power to beat your opponent shortly.
"Thunder King Rai-Oh" is an excellent addition to a beatdown deck not only because is it a level 4 monster with 1900 ATK, but it stops your opponent from searching and you can tribute it to negate a special summon, which is very effective against Synchro decks.
If your opponent has been able to survive further through the mid-game, "Wicked Dreadroot" makes an excellent finisher by crumbling the attack strength of your opponent's monsters. If your own monsters are weakened by this effect as well, sacrifice a DARK one to "Deck Devastation Virus", enabling you to clear the field for a swift Direct Attack.
"Honest" is a staple in most LIGHT Decks and is also very effective in LIGHT Beatdown Decks due to its ability to have your battling LIGHT monster gain ATK equal to the attack target's ATK until the end of the turn at the cost of sending "Honest" from your hand to the Graveyard.
An alternative is to use "Koa'ki Meiru" monsters. These tend to have at least 1900 ATK, and some have up to 2100 ATK for no Tributes. Their downside is that you have to reveal a card in your hand but they also have powerful anti-meta effects. They can be combined with "Begone, Knave!" in order to return them to your hand so that they aren't destroyed at the End Phase.
In a Deck with high-Level monsters, "Montage Dragon" works very well. Even using mere Level 4 monsters for the Summoning will result in a 3600 ATK beatstick, more powerful than most other monsters in the game. Tributing this card for the aforementioned "Great Maju Garzett" will allow you to Summon a monster with double the former's ATK, spelling potential disaster for your opponent.
Use "Burden of the Mighty" to lower the attack of your opponent's monsters to inflict even more damage or to give you an edge over your opponent's monsters that would normally be more powerful than yours.