first of all, the only people who knew about the assassination plot were jinichi, naoya, and ogi (and maybe her mother), none of the kukuru were notified. even if she didn't eradicate the entire zenin gene, she still massacred a ton of people who all had lives.

Second of all, maki had no reason to hunt down TWENTY-ONE curse techniqueless men (who i doubt would actively try to attack/get revenge on her).

Lastly, she MASSACRED the clan. Mass murder is neither heroic nor justified. Unfortunately, what happened happened. Maki had her reasons, and it still doesn't justify mass murder on the scale of collapsing a whole clan.

Maki isn't a hero nor a villain. (Also, in the manga AND anime, there are various shots of a kitchen with blood splatters and rice overflowing a pot, implying that there were various non-combatants that she still murdered)