いじijiめるmeruいじijiめるmeru
1.

To intentionally inflict suffering or distress on someone perceived as weaker, often for one's own amusement.

2.

To treat someone in a harsh or excessive manner beyond what is considered reasonable or just.

3.

To bother or harass someone with persistent taunts or teasing, causing emotional discomfort.

Example:

私は彼をいじめたことを後悔した。