Age of Empires II: Definitive Edition (PC) - Achievement - Against All
Defeat the Crusaders in the fifth Jan Zizka mission "The Emperor's Fury".
This achievement triggers on completion of the level so long as Crusaders (Yellow) are defeated. You have no villagers and have to rely on tribute from your ally and the spoils of your raids for resources.
Part way through the mission, this will flag as a secondary objective. It will also highlight the 10 Crusader locations on the map. For each location cleared, you will be rewarded with troops. Just make sure you've cleared all 10 before defeating Zawisza (Blue) and Emperor Sigismund (Red).