Learn Italian: Il vecchio inquilino ha lasciato la casa sporca.

Not necessarily! Because vecchio is placed before the noun inquilino, its meaning changes to indicate the former or previous tenant. If it were placed after the noun (l'inquilino vecchio), it would mean the tenant was physically old.

Why use ha lasciato instead of è partito for 'left'?

In Italian, lasciare is used when you leave a specific thing or person behind, meaning it needs a direct object. Partire (to depart) and andarsene (to go away) are intransitive verbs of movement and cannot take a direct object like la casa.

Why does sporca agree with la casa instead of the subject?

Sporca acts as an object complement here. It describes the state in which the direct object (la casa) was left. Therefore, it must agree in gender and number with the feminine singular la casa, even though the subject doing the leaving (il vecchio inquilino) is masculine.

Why doesn't the past participle lasciato agree with the feminine object la casa?