Flex

Verb - to show off, instill jealousy and a sense of inferiority on others whether intentional or not.

Also, a word to give powerless people the feeling of power by granting them the feeling of being in a higher moral ground of 'humility' (by keeping quiet, most of the time, to protect their own ego in case someone superior makes them feel worse), and hence the perceived moral authority to insinuate people as malicious narcissists regardless of the true intention of the person sharing the experience.

The word is used in both attack (insult) and defense mechanisms.

As an attack, to guilt trip and label a person's action as malicious for making other people around them potentially feel worse about themselves, regardless of the actual intent.

As a defense, to distract a person from the realization of their own inferiority, by insinuating that the other person is a narcissist, thereby shifting the battle from a battle of 'who is skillfully superior' to 'who is morally superior', taking the person using the word from a position of loss due to worse skills, to a winning position by thinking of themselves as humble and non-malicious for keeping quiet.

The word is easy to use, doesn't require high emotional intelligence, and absolves the user of responsibility for causing emotional hurt to the other person they use it on due to the frequency of use in popular culture.

Example 1:
A (Cheerful Person who generally just likes to share things they like, slightly insensitive)
B (Has insecurities about their achievements, often compares themselves to other people)

A: Hey! My Aunt treated us to this nice buffet place last night!
B: Woah... FLEX!
A: How is that flexing?
B: Because we all wanted to go buffet yesterday but we couldn't! Now you made us all feel jealous and poor!

Example 2:
C (Doesn't care what others think, does things on his own and does very well in them)
B (Has insecurities about their achievements, often compares themselves to other people)

C: *Presents the work he's been doing solo on his own for the past 3 months, while everyone else has been slacking*
B: *Whispers to a friend* Oh my god, this is such a market spoiler. Is he trying to flex towards the Professor?
C: *Doesn't actually care what anyone thinks, he just enjoys what he's doing and does very well in it*