Resentful describes feeling angry or bitter because you think you have been treated unfairly. The feeling usually lasts and can grow stronger over time.
From French *ressentir* meaning 'to feel strongly', based on Latin *sentire* 'to feel'. Over time, English narrowed it to strong negative feelings about being wronged.
Resentful emotions are like emotional leftovers—they stick around long after the event is over. The danger is that resentment often hurts the person who carries it more than the person who caused it.
Complete word intelligence in one call. Free tier — 50 lookups/day.