Hi!
Colonist settlements on Powhatan land caused many, many, MANY problems.
The first one is the most obvious-- the colonists were taking Powhatan land, which none of the Powhatans were happy about-- thus disputes over land began to break out. The Powhatan Chief attacked the colonists because he realized that the colonists wanted complete control over the land. The colonists, in return, threatened to destroy all of the Native Americans. The colonists had an edge in this point-- they had guns, whereas the Powhatans did not.
Land disputes and wars were only the beginning-- one of the greatest killers of Native Americans was the disease that the colonists brought over, like syphilis. These diseases killed a vast majority of the Native American population.