People can have crab mentality for various reasons, such as because they’re trying to feel better about themself, because they view other people’s progress as coming at their own expense, or because they see others displaying the same kind of mentality.

The main sign of crab mentality is that someone often tries to discourage or sabotage others, in cases where there are no direct benefits to doing so.

• The tall poppy syndrome, which describes a phenomenon where people disparage those who do well.
• Schadenfreude, which is satisfaction that’s derived from someone else’s misfortune.
• The mentality of “if I can’t have it, neither can you”.
• Various idioms, such as “misery ...