vital strike

You brandish the weapon used in the spell’s casting and make a melee attack with it against one creature within 5 feet of you. On a hit, the target suffers the weapon attack’s normal effects and the attack becomes a critical hit on a 19-20.If the attack becomes a critical hit the target becomes poisoned until the end of your next turn.

At 5th level the attack crits on a 18-20,17-20 at 11th level and,16-20 at 17th level.