So-called 'Battle of Faesulae' (406 CE).

[Flavivs Aetivs]

Attila's army probably numbered around 80,000. The only surviving mention of its size (other than Jordanes who is... well... Jordanes) survives via a garbled acouunt of Priscus in the Suda which states it was in the "tens of thousands." That, along with of course Aetius' "Not unequal" force, were the two largest armies assembled in the 5th century.