extenuate

ɪkˈstɛnjʊeɪt
ɛkˈstɛnjʊeɪt

verb

cause (an offence) to seem less serious.

even the fact that you once helped to save my life could not extenuate your offence

excuse,mitigate,palliate,make allowances for,make excuses for,defend,vindicate,justify,explain,explain away,give an explanation for,make a case for,diminish,lessen,moderate,qualify,soften,play down,reduce,temper,weaken,mitigating,excusing,exonerative,palliating,palliative,justifying,justificatory,vindicating,exculpatory,moderating,qualifying,softening,tempering,diminishing,lessening