Sinful

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Old English synfull (see sin1, -ful).

wiktionary

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From Middle English sinful, synful, senful, sunful, from Old English synful(“sinful, guilty, wicked, corrupt”), equivalent to sin +‎ -ful. Cognate with Dutch zondevol(“sinful”), German sündevoll(“sinful”), Danish syndefuld(“sinful”), Swedish syndfull(“sinful”), Icelandic syndfullur(“sinful”).

etymonline

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sinful (adj.)

Old English synnfull "full of sin, wicked, unholy, contrary to the laws of God;" see sin (n.) + -ful. Weakened sense of "contrary to propriety or decency" is from 1863. Related: Sinfully; sinfulness.