Learn Spanish (Latin America): Me sorprendió que el empleado no hubiera mostrado dedicación. - It surprised me that the employee had not shown dedication.

We need the past perfect subjunctive (hubiera mostrado) because the action of not showing dedication happened before the feeling of surprise. If you used the imperfect subjunctive (mostrara), it would imply the lack of dedication was happening at the exact same time you felt surprised.

What triggers the subjunctive mood in this specific sentence?

The verb sorprender expresses an emotion or subjective reaction. Because the main clause expresses a reaction (Me sorprendió) to a new subject's action (el empleado), Spanish requires the subjunctive mood in the clause that follows que.

Why does the sentence start with Me instead of Yo?

The verb sorprender works similarly to gustar. The literal structure is closer to "It caused surprise to me." The entire idea of the employee not showing dedication is actually the grammatical subject of the sentence, and Me is the indirect object receiving the feeling of surprise.

Where exactly does the negative word no go when using a compound tense like this?