This list isn't really fair. Mosquitoes don't actually kill people, they are just vectors for a disease which does kill people. So then humans should get a point for every death due to flu, AIDS or COVID-19, right? And all the accidental deaths too, because I'm pretty sure the mosquitoes are just living and don't intend to kill anyone. So I think human should be number 1 by a very long way, followed by mosquito.