As the army of the dead march on Winterfell, the forces that have aligned with Daenerys and Jon Snow to fight under their orders probably all have the same question on their mind — what exactly are they up against? The citizens and soldiers at Winterfell have surely heard about the coming threat of the undead, but only a few people behind Winterfell's walls have actually seen the supernatural threat. While the wight's powers in Game of Thrones don't amount to much, the sheer volume of them — not to mention the fact that every dead person can be turned into a wight — could spell problems for the citizens of Westeros.
Anyone familiar with what are generally accepted amongst various adaptations to be the "rules" of zombies already has a pretty complete idea of how the wights function in Game of Thrones. They're raised from the dead, and have a will of their own — usually to kill — but also act under the orders of the Night King and his White Walkers. While the Night King's powers should be enough to strike fear into the heart of any many, the wights powers seem to simply be that death tends to elude them.
Wights, and even their disembodied limbs, can continue to fight until they are set on fire, or the White Walker that raised them from the dead is killed. Wights themselves are highly flammable, making dealing with one of them simple if flames are easily accessible. However, if someone were to find themselves without a flaming sword or a torch and surrounded by wights, one's chances of survival suddenly becomes a lot less likely.
Other than how hard it is to kill them, the wights really don't have any advantage over humans when it comes to sheer physical strength. However, it can be argued that they're true superpower is a willingness to die and a lack of care for the lives of their fellow soldiers. While Jon Snow has proven himself to be an accomplished fighter, his emotional connection to the people he's fighting for has led to some bone-headed decisions that have gotten other people killed. An emotionless army that seems to have an unlimited number of men can actually risk having people make those bone-headed decision without losing something more than a physical body that can throw a sword around and pierce the flesh of the living with their teeth.
The wights pale in comparison to the White Walkers when it comes to powers and ability, but there's no discounting the sheer scope of the wight army. Even the Dothraki and the Unsullied combined may not be able to stop an army that never gets tired, cannot be killed by physical violence, and is constantly gaining new soldiers as the White Walkers resurrect the dead. The wights may not have many powers beyond being able to fight after getting one's arm cut off, but that doesn't make them any less of a threat to the citizens of Westeros.