Invisible Woman is much more closely associated with the Fantastic Four than the Avengers, but that's not to say she won't answer the call alongside the rest of Earth's Mightiest Heroes when necessary. Sue often tends to serve as the heart and soul of any team she serves on. Her power to manipulate invisible force fields arguably makes her the strongest of the FF. But despite that power she remains firmly grounded in the real world.
She keeps her dysfunctional family in order, whether it's dragging her husband and daughter out of the lab or making her hotshot brother act his age. Sue is a matriarch who isn't at all afraid to kick some ass when the situation calls for it. And the Avengers' villains have come to realize that every bit as much as Doctor Doom or Galactus.