Looks like somebody punched the lower right corner of your screen. Ive never seen a GFX card die like that. Ive seen them die one pixel at a time. ive seen them die Etch a sketch style, but never like that.
if all else fail............ put the card (without the cooler and other plastic bits) into an electric oven middle shelf at 385 f degrees for about 8 minutes keep the metal away from the card if the problem is heat then this should reset the solder this has worked on three out of eight that we've tried all good cards