Evil Helps Good

If Evil Helps Good, does that make it less evil?

When evil provides assistance to good. This can be permanent or temporary and can come in many forms. The most common form is if the Bad Guys join the Good Guys because their cause is either a threat that affects many people, including the Bad Guys, or an enemy of theirs who isn't the Good Guys has done something wrong to them (such as kidnap one of their teammates or attack their base) and they figure that the only way to get revenge is by siding with the Good Guys so they can team up on their enemy. A less common reason why Evil Helps Good is because the Good Guys first helped the Bad Guys with some selfless deed which they want to repay the protagonists for.

Evil Helps Good may be considered a Plot Saver as the Good Guys need someone to provide assistance as, for example, they're behind enemy lines in a conflict, but all of their friends are either defeated or unavailable at the moment, so a member of the opposing force must change their ways and decide to help the Good Guys in need. Later, this evil-gone-good Traitor may be caught by one of their superiors and disowned right on the spot with no chance of redemption.

Note that for this UnTrash to apply to a scene, the Bad Guys must genuinely want to aid the Good Guys in their battle against the enemy, so if they want to trick the Good Guys into thinking they're helping, this UnTrash isn't for that scene. Deceptive Partnership would instead be the proper UnTrash.