The Absol Doom News attack states that the Defending Pokemon is knocked out at the end of the Opponent's turn. If the Active Pokemon is switched, does the Defending Pokemon stay the same, or does the new Active Pokemon become the new Defending Pokemon? Is this attack unstoppable?
Like most effects that are applied to
the Defending Pokémon, this effect is removed if the Defending Pokémon leaves the active slot (or is evolved/devolved). So if you retreat/switch Pokémon, no pokémon is knocked out by the effect.
From the Compendium:
Q. When I use Absol [G]'s "Doom News" attack, is my opponent's Pokemon still Knocked Out if they retreat it during their next turn?
A. Since it is an attack effect on the Defending Pokemon, it is removed if that Defending Pokemon is no longer Active. (Supreme Victors FAQ; Aug 27, 2009 PUI Rules Team)
If the intent was for it to apply to whatever Pokémon was in the active slot it would say something like, Next turn, knock out your opponent's Active Pokémon.