Burn through defense trait On my phone so a bit hard to post trait if my opponent has access to both impervious and invincible will he be forced to use invulnerability instead?

BURN THROUGH DEFENSES: When Atrocitus attacks a character that's using Impervious, this turn that character uses Invulnerability instead. When Atrocitus attacks a character that's using Invulnerability, this turn that character uses Toughness instead.

He would be forced to use Invulnerability instead of Impervious. Since the power does not mention Invincible it would be unaffected.

To further clarify what Quebbster is saying...

In the OP example, Impervious and Invincible would both be in use. So Atrocitus would turn that into Invulnerable and Invincible.

This then brings you to the choice of two competing effects as laid out on p. 10 of the rulebook...
Since the defender can only activate one effect that reduces damage, he would have to choose which one kicks in. It would still be the defenders choice.

Thanks so incase the opponent has both impervious and invulnerability would they only be able to use toughness?

They would be able to use either Invulnerability or Toughness. Opponent's choice.

Altho I am not certain, I would agree with Red King. It looks like both would be replaced by their lesser and then the character's controller would choose which would be used.

By atrocitus attacking a character that currently has those 2 powers imperv and invul does that not cause so would they still be able to choose between invul and toughness? And not just toughness? Sorry just tons of questions I got

The character would be able to choose between Invulnerability and toughness since the Invoulnerability it could allready use is replaced by touhhness. Thereby it no longer has invoulnerability from two sources.