In SH3 Heather points out that Alessa could kill people just by wishing for it. But, for her to know that, she, as Alessa, had to have done it, at least once.
Or maybe she didn’t, in the original Silent Hill, we see that Dahlia, who isn’t born with any (or at least with not very strong) powers, calmly using telekinesis and psychic shields, powers which belong to Alessa. However, she hasn’t demonstrated any of those powers before the Flauros was used. So, from that we can assume that Dahlia drains Alessa’s powers with Flauros and uses it to temporarily give herself her daughter’s powers.
We see something to that effect happening in the flash-back.
And...C’mon! C’mon! I just want you to lend me a teeny bit of your power, that’s all.
...
It will make everyone happy, and it’s for your own good too
The point is we see the in-game evidence that Dahlia and her partners in crime used Alessa’s powers for something. We also know that people involved with the development of the town started mysteriously dying, and that the anti-drugs mayor died from the heart attack, as did the narcotics detective Gucci.But the power we could draw from her now would be weak. Almost nothing
Alessa had no reason to want those people dead, but Dahlia and Kauffman did.
However, we never see any in-game evidence that Alessa never consciously killed anyone.
Or maybe we do? I don’t really know. My theory is that Dahlia, using Flauros and Alessa’s powers, went around killing people, not Alessa. However, if there are any evidence that Alessa did in fact kill someone, feel free to share.
Man, I seem to have a real talent for writing a lot, and yet saying so little... Sorry about that .