Quoted From My brother. it always helped me understand a few tricks in real life and online gaming.
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In Yugioh, there are duels that can be easily won in about 3-4 turns.
Sometimes it might take 7-11 turns if you’re not drawing the right
cards. However, some duels can take an eternity to finish or can be
lost, if your opponent summons their ace monster. Though spells and
traps help you throughout a duel, it is ultimately the monsters that
will deal the most damage. So therefore, many spells, traps, and monster
effects are used for protecting an ace monster. So how can you overcome
a strong monster if your opponent is using everything in
their repertoire to prevent that scenario from happening?
Destroying tough monsters isn’t easy. For a monster to be labeled,
’strong’, it’s got have powerful stats and a powerful a effect(s). So
destroying ’strong’ monsters isn’t always a task that can be done in a
couple of turns. Usually, your opponent will not have what I like to
call an Ace deck. This deck’s sole purpose is to easily summon
and protect the ‘ace’ monster of the deck. An example is the deck that
Yubel uses against Jaden in the final duel of Season Three of Yugioh GX.
The main purpose of her deck was to summon the Yubels and completely
seal them from destruction. If your opponent does have an ace deck, then
they will mainly be using cards that counter spells, traps, and monster
summons.
If your opponent does use an ace deck, you must use a counter ace
deck. This deck consists of strong level three monsters, such as Jerry
Beans Man. This deck revolves around the usage of cards like Gravity
Bind and Level Limiter B. Of course, you must also have cards like
Mystical Typhoon and Dust Tornado in order to counter
spells and traps that would threaten to destroy your level limiter cards
(Gravity Bind, Level Limiter B, etc…). This way, all of your opponent’s
ace monsters (which would most likely be monsters with six levels or
higher) would not be able to attack and would be sealed off. Of course,
cards like Yubel would be unaffected by this deck.
If your opponent does not use an ace deck, then more than likely they
will not have as many spell/trap counters and you could destroy their
ace monsters via spell, trap, monster effects, or by battle (if you can
pull out a strong enough monster). Don’t surmise what kind deck your foe
has based on their first turn. Every turn, sift your opponent’s card
patterns, then conclude what type of deck your opponent has and counter
it.
Subject: Yugioh Defensive Tactics 
