Relationship friction, duty and responsibility, power struggles, ego-related conflict

The character being told their outfit or hairstyle is out of fashion
A physical disfigurement being made fun of
A rude gesture, profanity, or hateful words being hurled at the character
A younger person assuming an elderly character can't make decisions for him or herself
Being dismissed by someone because of assumptions about the character's intelligence, integrity, or abilities
Being treated as less than (being denied the same level of service that others are given, being disrespected, others assuming the character shouldn't be allowed where they are, etc.)
The character being subjected to insults relating to their race or religion
Being belittled through ongoing verbal abuse
Experiencing insults via brainwashing, gaslighting, or other deliberate attempts to alter the way the character sees him or herself

The character returning the insult and escalating the situation
A child or impressionable character witnessing the insulting behavior
Being uncomfortable around the insulter in future interactions
Having to report the insulting behavior to a parent, boss, or authority 
The character avoiding places where they might run into the person who insulted them
Friends or family being dragged into the confrontation
Seeking out an apology and it not being granted
Reacting in a way that lowers the character in the eyes of others
Telling a trusted friend, who then downplays the incident or tries to rationalize what happened