OTK with Fenriloogamon
Condition for the OTK at the beginning of your turn: Have Eiji on field, an ultra level digimon on field or raising, BlackGatomon in trash or any digimon on field, 3 level 4 or lower Digimon in trash (including the BlackGatomon if no digimonn is on field) and Fenriloogamon in hand.
How to: Promote the ultra and mind link Eiji onto it. Digivolve Fenriloogamon on top of it. The when digivolve effect triggers and brings back 3 digimon from trash including the BlackGatomon. Swing with Fenriloogamon, alliance (from Eiji) suspends one of the returned digimon and its own attack trigger removes potential blast digivolve targets and unsuspends itself. Check 2. Swing again with Fenriloogomon, alliance again and use the inherit from either ultra to unsuspend again (it does not matter which suspended digimon is deleted for this). Check another 2. Swing again for the last check. Swing with BlackGatomon for game as it has rush.
OTK with Titamon
Condition for the OTK at the beginning of your turn: An ultra on field or raising, any digimon on field or playable from hand and any digimon in hand, field or trash either of which is BlackGatomon, and Titamon in hand. Opponent on only 4 or less security.
How to: Promote the ultra and digivolve into Titamon. Use its when digivolving effect to trash a card in hand and play BlackGatomon for free. Second ability triggers to give Security A. +1 and +2000 DP. Swing for 2 and use the inherit from either ultra to delete the left-over digimon to unsuspend. Check 2. Swing again to check another 2. Swing with BlackGatomon for game as it has rush.
The line with Titamon is not a proper OTK as it requires to have done a check beforehand and requires more memory at the beginning of the turn (4 instead of 2), it is however the best additional mega to run that I have found.
If anyone has any ideas for improvements, please let me know.