The first thing that comes to mind for me is to find some way in which they have impacted the current world, and relate him to that in your opening line. Perhaps he made an important discovery which everyone now knows, or perhaps is the basis of some modern piece of machinery. Much of this sort of information would be listed in a "fun facts" section on the subject.
As an example, this is how I would open a biography on Archimedes:
"It is said that Archimedes, one of the great minds of Ancient Greece, invented the practice of measuring volume by water displacement when he was taking a bath. He had been commissioned to find the volume of a crown of gold, but struggled to find a way to measure the irregular object. Then one, day, as he entered the bath, he took note of the water rising in proportion to the amount of his body submerged. It is said that he ran from his bath and through the streets naked, screaming, "Eureka, Eureka, I've done it!" While the accuracy of the events are unknown, and it is unlikely that Archimedes coined the term "Eureka" as the story suggests, it is widely acknowledged that Archimedes was the first to popularize water displacement, which became the standard practice for measuring irregular solids for over a thousand years."
(Ideally yours wouldn't be quite so long, this one just took a bit of explaining.)
After that first contribution is explained, you can transition into describing the other fields in which he made contributions, including far less detail. This method allows for your opening to be interesting and unique regardless of the subject of the biography, while also indicating why we should even care about this person.