As in consciously killed.
I slaughtered many types of fish,
atleast a billion insects,
two birds via airgun (never again)
put a frog on a barbecue (he hopped a few times)(regret)
tapped praying mantis on a firework rocket (explosive type)
electrocuted a few mice by putting wires by the hole (i quite that and merely trapped them and brought them to the neighbours)
and a dog while driving. (inevitable)