Idk what the worst is but yeah I'd like us to systematically hunt down every mosquito on the planet and render them extinct. Most likely by releasing some into the wild that introduce genes which lead to sterility in a few generations and just keep doing this until they no longer exist.

I'm probably coming from a different perspective. Because I don't really care if they're sentient or not. If they have evolved to be a parasitic organism that spreads disease and whatnot through other species I see no problem with simply wiping them from existence. So long as we do it properly and study the impact it will have on the wider ecosystem, and I've seen studies that say their extinction wouldn't have a very big impact. Those might be wrong though. I'd want us to make absolutely sure before actually doing it.