Is killing her the worst? or it makes the MCU unpredictable, that no hero is safe. The problem with the avengers and mostly the MCU they do not kill anyone off, that is the big problem with it and this hurts the villains, the villain never has its day. Its not killing hero's off for shock factor, its balancing out the stages and creating an edge that the villain is a threat. Has we get closer and closer to infinity wars, if we have way too many hero's alive, it becomes a cluster****.
Am I saying kill everyone off? no, what I am saying is, you cannot keep having these films if the villains says some stuff, and kills no one, hell loki kills one of the agents and he is brought back anyway. Its probably what made AOU a little bit different, they did kill a hero, so I will give them credit. But on some levels, a war machine, falcon, black widow, in the future vision should be taken out of the game. If throughout the MCU we get no hero deaths, its a big copout playing it safe to please everyone