How to Say "anyone who" in Spanish
The Spanish word for “anyone who” is “quienquiera” — C1 level.

Examples
Quienquiera que haya tomado mi libro, debe devolverlo inmediatamente.
Whoever took my book must return it immediately.
La ley protegerá a quienquiera que denuncie la corrupción.
The law will protect anyone who reports corruption.
El premio será para quienquiera que demuestre el mayor esfuerzo.
The prize will go to whoever demonstrates the greatest effort.
Always Use the Subjunctive
Because 'quienquiera' refers to an unknown or hypothetical person, the verb that follows must be in the special verb form (the subjunctive). This is necessary to show uncertainty.
The Optional 'que'
You almost always need to follow 'quienquiera' with the word 'que' before the next verb, like in the examples: 'Quienquiera que llame...' ('Whoever calls...').
Using the Normal Verb Form (Indicative)
Mistake: “Quienquiera que *llama*...”
Correction: Quienquiera que *llame*... (The verb *llamar* must change to the subjunctive form *llame*.)
Related Translations
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