Probably. But it's also a bit of a difficult question to compare the two.

One prominent estimate is that about half of all humans who have ever lived died from mosquito-related illness, about 50 billion of the 100 billion humans who have ever lived.

For humans, it's estimated that about 3-4% of paleolithic humans died from violence at the hands of another person, and that number may have risen to about 12% during medieval history, before plummetting in the modern age.

But that's the comparison of direct violence versus illness. Humans have a strong capacity to indirectly cause death, including by starvation, illness, indirect trauma. How do we count deaths from being intentionally starved as part of a siege? Or biological weapons, including the time the Nazis intentionally flooded Italian marshes to increase malaria? Do we double count those as both human and mosquito deaths?

And then there's unintentional deaths, caused by indifference or recklessness or negligence. Humans have caused famines, floods, fires, etc.

So yeah, mosquitoes probably win. But don't sleep on humans. And remember that the count is still going on, and humans can theoretically take the lead in the future.