Possession basically instantly removes one enemy from the fight, redirects fire away from you and does potentially heavy damage to all other participants in the fight. It's crowd-control, a diversion and an insta-kill in one. The only arguable draw-back this thing has is the cost, which gets mitigated later in the game.
On difficulties higher than Normal, I can't fathom why anyone would even bother using any of the other Vigors.
On difficulties higher than Normal, I can't fathom why anyone would even bother using any of the other Vigors.