Tom felt that pressure of the heart which forbids tears; he had no distinct vision of their troubles as Maggie had, who had been at home; he only felt the crushing weight of what seemed unmitigated misfortune.
There are no more uses of "mitigate" in the book.
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Don’t judge her so harshly until you consider the mitigating circumstances.
The new factory is building privacy walls to mitigate its impact on neighbors.