The exalted ability triggers when a creature attacks alone.
From the Comprehensive Rules (April 12, 2024—Outlaws of Thunder Junction)
- 506.5. A creature attacks alone if it’s the only creature declared as an attacker during the declare attackers step. A creature is attacking alone if it’s attacking but no other creatures are. A creature blocks alone if it’s the only creature declared as a blocker during the declare blockers step. A creature is blocking alone if it’s blocking but no other creatures are.
From the glossary of the Comprehensive Rules (April 12, 2024—Outlaws of Thunder Junction)
- Attack Alone
- A creature “attacks alone” if it’s the only creature declared as an attacker during the declare attackers step. A creature “is attacking alone” if it’s attacking but no other creatures are. See rule 506.5.