Not stained, spoiled, or damaged; pure and clean in reputation or character.
From un- (not) plus sullied, the past participle of 'sully' from Old French souiller (to soil), from Latin sucus (juice or liquid that soils).
Unsullied is the kind of word you'll find in fantasy novels describing noble heroes and pure kingdoms—it has an almost too-perfect, storybook quality, which is why modern writers often avoid it because real people and things are rarely so pristine.
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