Final answer:
At the Battle of the Catalaunian Plains in 451 AD, the general who lost his only battle was Attila the Hun.
Step-by-step explanation:
In 451 AD, at the Battle of the Catalaunian Plains, the general who lost his only battle was Attila the Hun.
Attila the Hun was a fearsome warlord who led his armies against Rome in the 5th century. He was known for his military tactics and his ferocity in battle.
Although Attila was successful in many of his campaigns, he met his defeat at the Battle of the Catalaunian Plains, where he faced a combined army of Romans and their allies.