Since you think it’s wrong to kill anything that’s alive, I’m assuming you don’t eat anything? Plants are alive and animals aren’t just alive, they are sentient too.

I think in most cases of abortion we are dealing with a nonsentient being, so it’s not immoral to kill it. Even when it is sentient, I think that negative rights override positive rights. A fetus cannot stay alive without relying on the woman that is pregnant with it. Women have a right to bodily autonomy. So, if a woman refuses to let a fetus live off her body, that’s within her rights. The same way no one is entitled to your spare kidney to live, a fetus isn’t entitled to a woman’s body. You might be in effect “killing” the individual whose life was dependent on you, but you aren’t taking anything away that belonged to them.