I crushed a snail with my foot and it made a crunch
It is a living thing! Why didn't you just step over the snail?
This is not the first time this happened. I hurt other creatures intentionally.
There a valid reasons for killing creatures. It's not good to kill them for no reason because many have a purpose in the web of life -- they're doing important work, like pollinating flowers and crops, breaking down garbage, etc.
What if I hurt other creatures on purpose because I hate them?
That unfortunately can be a sign of sociopathic behavior, and if you're really concerned then I suggest to try and have an appointment with therapy to sort all of this out. Animals are living creatures, they only have one life just as you. They deserve to live out naturally.