誰がこの窓を壊したの？

who

indicates sentence subject (occasionally object); indicates possessive (esp. in literary expressions); but; however; still; and

this (something or someone close to the speaker (including the speaker), or ideas expressed by the speaker)

window

indicates direct object of action; indicates subject of causative expression; indicates an area traversed; indicates time (period) over which action takes place; indicates point of departure or separation of action; indicates object of desire, like, hate, etc.

to break; to destroy; to demolish; to wreck; to ruin; to spoil; to damage; to break (a bill, etc.)

indicates possessive; nominalizes verbs and adjectives; substitutes for "ga" in subordinate phrases; (at sentence-end, falling tone) indicates a confident conclusion; (at sentence-end) indicates emotional emphasis; (at sentence-end, rising tone) indicates question