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The titular character of Stephen Sondheim's Sweeney Todd, after being sent to a penal colony for fifteen years on a trumped-up charge, returned home to find that his wife had poisoned herself (though contrary to what Mrs. Lovett would have him believe, she's still alive) and his daughter was adopted by the man responsible for his suffering, and, failing in his big attempt at revenge, finally goes Ax-Crazy and becomes this at the end of Act One.
From the same musical, Audrey applies even moreso. Not because she contributed more to the destruction of the world, but because she's even more of a Woobie. Her dying words made humanity's salvation impossible - entirely by accident.