The superlative form of rugged, which means very rough and uneven, often in a strong and attractive way.
Ruggedest makes people think of wild places and strong things.
Examples:
The mountain is the ruggedest of all.
He is the ruggedest man I know.
The path is ruggedest here.
She is the ruggedest hiker in the group.
The ruggedest rocks are the hardest to climb.
The bear is the ruggedest animal in the forest.