Who destroyed the Gupta dynasty?

As per several historians, the Gupta dynasty and by extension the empire itself, disintegrated due to attacks from the Hunas (Huns) under Toramana and his successor Mihirakula. Although their power was diminished, the Guptas still continued to resist the Hunnic invasions.

For further reading check the following articles:

• Facts about Gupta Empire
• Decline of the Gupta Empire