Akampana was one of the demons and a trusted lieutenant of
Ravana. He was killed by Hanuman in the Ramayana. It is mentioned in the Sarga
56, Yuddha Kanda of Ramayan.
When Rakshasa Dhoom Raksha was killed by Hanuman, Ravana asked
Akampana to enter the battlefield.
He led a vast army of demons and fought fiercely against the
Vanarasena (monkey army). But majority of the demons were killed by the
Vanarasena headed by Hanuman.
Akampana was furious and started attacking monkeys like a mad
man. Hanuman countered him barehanded.
Hanuman threw a huge boulder on Akampana. The demon reduced the
huge stone into powder with his arrows.
Hanuman then uprooted a tree and whirled it like a wheel
killing many demons.
Akampana sent fourteen arrows at Hanuman but they were all
blocked.
Hanuman then uprooted another huge tree and hit Akampana on
his head.
This resulted in the death of Akampana.