Not sure if this has been asked before but, I find the wording on Omnitron character card a little odd. It states: “When Omnitron is destroyed, remove Omnitron’s villain character cards from play. The heroes cannot win until there are no devices in play.” However, the act of removing Omnitron’s character cards from play also removes the line “The heroes cannot win until there are no devices in play.” from play. Hence, the condition fizzles and the heroes win?
Other examples, Kaargra Warfang’s character card reads: “The Heroes cannot win the game.” Once she flips, the text is no longer in effect, and the heroes can win.
The setup card still remains out which is why that works. In the case of Kaargra only one side of her setup card says the heroes can't win. The oversized cards do muddle this up a bit but the setup text remains in affect.
Both of Omnitron’s cards are removed. The reason it works is because a specific ending specified on the card. Take The Wraith’s Throat Jab, it remains in effect even with the card no longer in play because it says when I ends.