Reluctant or refusing to forgive.
An unforgiving creditor.
Not willing or not able to forgive.
Not allowing for error or shortcomings, especially in being harsh.
An unforgiving climate.
Allowing no room for adjustments or for errors or weakness; inflexible, exacting, harsh, etc.
An unforgiving budget, unforgiving climate.
Origin of unforgiving
un- +"Ž forgiving