[Nyx]

A patch of burn in if it's an OLED, or ~10 dead pixels if an LED should be relatively easy to Photoshop. Not exactly a dead panel, but is enough damage to usually fall under warranty. Very common issues from companies with even the best of QC policies as well.

what if they ask you to send the monitor back?

That's an entirely different situation, likely an EB. The OP is looking for ways to convince them that his monitor is defective and not a power issue.