Risa

Honestly, Archer's is by far the least evil in those examples.

Sisko used chemical weapons against a civilian target because he felt wronged by one specific guy he worked with for a short while, who ended up being a terrorist, and Sisko really didn't like that it was going on under his watch.

Janeway killed someone who had done nothing wrong and was kneeling on the ground crying and begging not to be killed, against the doctor's judgement, because she knew that killing this innocent person would bring a close friend back.

Archer, by force, stole components of a ship, fitted crappy ones in turn, vastly reducing the speed of an alien's ship to the point it'd likely take them years to get home. He acknowledged it was an evil thing to do, but the alternative was to knowingly let Earth be entirely destroyed. Every person, every animal, all Earth culture, gone in a planetary holocaust. After he did it, he was shown to be grappling with the guilt - Janeway and Sisko weren't.

Now, having the cure to some disease that appeared set to wipe out a species, and being so easily convinced not to give them it by the ship's doctor? Now that's evil Archer.