Ladder Kicker
A person who thinks they're special just because they got to the top, so they kick the ladder out from under everyone else to keep their spot.
I made it to the top, so I’m kicking the ladder away. No one else can be good anymore.
She got the promotion, so she trashed the office. Everyone else is doomed.
He’s at the top now, so he’s making sure no one else can climb up. Ever.