Thanos
With the defeat of Proxima Midnight Wanda returns to Vision. To protect as is her mission.
"Wanda, you have to destroy the stone" Vision tells her
"No, we don't trade lives. My job is to protect you and that is what I will do" Wanda tells him
"Not at the cost of everyone else" Visions tells her
Wanda looks back and see's everyone battling Thanos. Vision's right she can't loose her family. Some of them are here fighting and others are at home. She needs to protect them and unfortunately that means she has to destroy the stone and Vision with it.