This was by far Cassie's worst sin, erasing someone from existence. And if like me, you believe in the concept of a soul or an afterlife, then this just doubles the horror of basically destroying someone's soul, so that they cannot even have a peaceful death.
But was it really necessary? Let's talk about that. I mean, the Animorphs had possession of the Time Matrix. They could have gone anywhere, any time, and honestly, erasing the host body of Visser Four makes no sense, since he would have another host body, and if he got reassigned to Earth, he'd have another human host and end up going to the construction site and discovering the Time Matrix for whatever reason he did in the original timeline. Honestly, this feels like Cassie's darkest sin simply being there just to be the most evil thing she's ever done. Couldn't the Animorphs have used the Time Matrix to travel to the moment just before Visser Four found the Time Matrix. Even killing him to prevent that future from happening would be better than just causing a man to cease to be.
Thoughts?