Not sure if this is a bug or just a wording issue.
Kitty’s red countdown tile was on the board, and the enemy fired their teamup power, doing damage to Kitty. No attack tiles were created.
In this case, the teamup was 1* Hawkeye Arrow Stab, “Clint lunges forward, arrow in hand, clearing a selected row and dealing damage”.
So either there is a bug somewhere, or Kitty’s red works only if kitty or a teammate is injured by the direct damage component of an enemy power, not just if they take “damage from an enemy power”.