All along on the path to Victory!!

For many years UY Scuti was considered the largest known star in the universe. Then came along the behemoth that is Stephenson 2-18. But it turns out that measuring enormous, distant, bright stars isn't easy, and both UY Scuti and Stephenson 2-18, although very big, are probably not as big as initially thought. So by using the best measurements available, what is the current largest star in the known universe?