I'm looking for the word to describe for someone who's so insecure about being the best, that they would go to great length to sabotage other peoples chances just to be the best.
For example, Lisa Simpson is known for this because whenever someone is better than her at something (music, school etc.), she'll get jealous and try to sabotage them.
Another example is Jerry Smith from Rick and Morty, who was willing to risk a whole eco system just to pretend he's right (pluto being a planet).
The word I've heard over the years was pretentious (attempting to impress by affecting greater importance or merit than is actually possessed) but I discard it because I didn't see the sabotage others in it.