Looking for a word more formal than “hater” but with slightly different definition

Question

I'm looking for a word that describes Person A in the following situation:

Person A pretends to be friends with Person B but when B goes off to start a business, A secretly doesn't want B to succeed (possibly because A feels that only he should succeed and feels threatened by the success of others.)

"Narcissistic" could work but doesn't capture the insecurity of the person. "Jealous" and "envious" suggest that there is already some achievement to speak of. Similarly, being a "hater" typically implies that the hated person is already successful.

Answer 1

If Person A does not actually like Person B and wants him to fail, Person A is spiteful.

Spite via M-W

Petty ill will or hatred with the disposition to irritate, annoy, or thwart

If he believes himself above others and thinks only he should succeed, perhaps he is conceited.

Conceited via M-W

Having or showing an excessively high opinion of oneself

For someone who both has a high opinion of oneself and shows disdain for other's aspirations, they may be considered haughty.

Haughty via M-W

Blatantly and disdainfully proud : having or showing an attitude of superiority and contempt for people or things perceived to be inferior