If they roll up and tell you they're going to save your soul, you say: "Guys, I wouldn't trust you to save my credit card info."
~ Leah Cassini about the Templars.
Hold on, kids! I'm comin' to rescue the lot of ya! (gets axed in the back by Seymour Skinner) Ow! Ach, I'm bad at this! (dies)
~ Groundskeeper Willie

Heroes who are more likely to accidentally foil their own plots than the ones of villains they're fighting against, due to stupidity, bumbling, poor planning, cowardly behavior, weak strength, arrogance and/or unwillingness on their part.