There isn't a single, large island at 65 degrees north and 70 degrees west. This location is in the middle of the Atlantic Ocean, and the closest landmass is Greenland, which extends further north and west.

To be more specific, you need to consider the following:

* Greenland: This is the world's largest island and is located significantly north and west of the coordinates you provided.

* Iceland: This island is further south and west of the given coordinates.

* Smaller islands: There are some smaller islands in the Atlantic Ocean around that area, such as the Faroe Islands, but none of them are significantly large.

Therefore, you need to provide more specific coordinates or a different reference point for me to accurately identify the largest island.