'Titan Showdown' is a skill specifically used by Rex Raptor. It doubles damage dealt to your opponent as long as your LP is half or less than half of your opponent's current LP. Since Tea uses Solemn Wishes, it will be more convenient to make use of the 'Titan Showdown' skill. For example, if Tea's LP skyrocketed to 8000 LP, you can already fulfill the criteria of the skill.
To achieve the 'more than 9999 damage dealt' assessment, you can rack up the ATK of Millennium Scorpion to at least 5000 ATK and land a direct attack with it.
Starting the duel
Since all no-tribute monsters in this deck are all level 4 monsters, you can start off by summoning one of them into the field. You can easily use Insect Imitation to special summon Millennium Scorpion. Use Millennium Scorpion to clear Tea's monsters every turn.
Fitting the criteria of Titan Showdown
To double your direct attack damage, your LP must be half of your opponent's current LP. Since your opponent is Tea, this will be very convenient as she might activate Solemn Wishes to increase her LP to as high as double of yours. If this is not enough, you can use Amazoness Chain Master to lower your LP to fit the criteria more easily. It is mandatory to ensure that you fit the criteria of Titan Showdown before your last turn.
Precautions to take note of
Since Tea may use Cards from the Sky, she may deck out earlier than you do. So at the moment when her deck reaches 0, be very careful of her set cards as it might be a Skelengel. In this scenario, you may use Relinquished to safely steal it so that your Millennium Scorpion will be able to direct attack Tea provided that she has no other monsters.
The finishing blow
This phase is specifically for your last turn where either you will deck out on your next turn or Tea will deck out after your 'supposedly' last End Phase. You will need your Millennium Scorpion to hit at least 5000 ATK in order to achieve the 'more than 9999 damage dealt' assessment.