What was the most powerful of the Old Scandinavian kingdoms?

The most powerful of the Old Scandinavian kingdoms was often considered to be the Kingdom of Denmark, especially during the Viking Age and into the Middle Ages. Under leaders like King Harald Bluetooth and later King Canute, Denmark expanded its influence over much of Scandinavia, including parts of England and northern Germany. Its strategic location and naval strength contributed significantly to its dominance in trade and warfare during this period.