Despondency conveys deep sadness, more intense than just feeling down. His despondency was apparent to all who knew him well.
Pro Tip 2/3
Beyond sadness
It suggests a loss of hope or spirit, not just temporary unhappiness. After the team's fourth loss, despondency settled over the players.
Pro Tip 3/3
Serious tone
Despondency is a word with a heavy, serious tone, often related to significant life events. The novel's protagonist wrestles with despondency after the war.