Powers used against you will only deal half the damage they should normally do. Power-based flamethrowers will do less damage than normal flamethrowers. Resistance Increase also protects you from various forms of instant death, reality warping, and all forms of strange and esoteric effects. While it doesn't fully negate it, it makes it so it has less effect on you. To the point, you would survive a power that would normally kill you in an instant but only barely.
This can apply to Stranger, Trump, and Master powers as well. Although this power is less effective against All-or-Nothings.