How to stop Thanos.

Gather half of the Earth's resources into one place.

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Put a wooden building around it.

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Hold a lit match while standing on it. Have a few friends do it as a redundancy.

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If he turns any of you to dust, half of the earth's resources would be destroyed by the resulting flame, and so the entire point of his plan would be for nought.

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If he does the snap and none of you die, drop the match voluntarily. Same result.

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He can use the time stone once its verified that you'll actually do it, to go back and not do it.