You want invincible decks then? Decks must have a weakness, how is it fun going against something that can't be beaten? They don't use extra deck but remember koaki??
The mirror match: whoever goes second wins
Any other deck vs koaki: if you go first and you didn't draw canadia or floodgate it was an instant gg.
you don't need to go that far bro just remember six samurais they had an out to almost everything
traps? shi en negates
destruction? banish fuma in gy
floaters? return them to the hand with enishi
lava golem? syncro into castle next turn.
floodgated? go into the fusion
you had to play the same deck and go first or play that cipher soldier deck that would lose against everything else.