3 official rulings from Bandai, last ruled Sep 13, 2024. Straight answers to how this card actually resolves.

I tried to delete 1 of my other Digimon using this card's inherited effect when an opponent's Digimon attacked, but I couldn't delete the other Digimon due to another effect. Can I end that attack at such times?
No, you can't end that attack. If the "by doing X" condition isn't met, the rest of the effect isn't processed. In this case, if you can't delete 1 of your other Digimon, then you can't end the attack.
Ruled Sep 13, 2024
What does "end that attack" mean, exactly?
After this effect activates, the current timing makes a transition to the end of attack timing. For example, if this effect activates during the attack declaration timing, it will make a transition to the end of attack timing. A transition to the counter timing or block timing won't occur, and the attack won't succeed.
Ruled Sep 13, 2024
Can an "end that attack" effect end an attack by a Digimon that isn't affected by effects?
Yes, you can end such attacks. "End that attack" effects are effects that change the timing, they don't affect an attacking Digimon.
Ruled Sep 13, 2024
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Questions and answers are Bandai's official rulings, collected and translated by the DigimonCardGame Wiki community and reused here under CC BY-SA. Card names and card text are © their respective publishers; Combalo is not affiliated with Bandai.