noun
peccadillo
pek-uh-DIL-oh/ˌpekəˈdɪləʊ/
A minor fault or wrongdoing.
She overlooks his occasional peccadilloes because he usually treats people well.

Etymology
Pecado means 'sin,' and the diminutive makes it a 'little sin.' That reduced scale explains why a peccadillo is a minor fault rather than a grave offense.
More examples
- He considers taking an extra cookie a harmless peccadillo.
- Her memoir openly admits the peccadilloes of her youth.
- Stealing company funds is no mere peccadillo.
Forms
peccadillo · peccadillos · peccadilloes