One of the most memorable (and disgusting) Red Lantern powers is the ability to have vomit forth a projectile red goop.
During the New 52 era of DC Comics, the decision was made to approach Supergirl from a new angle. Rather than just being another Kryptonian, Supergirl joined the Red Lantern Corps.
The toll of fighting constant battles and living with the memory of her dead planet, has consequences. Kara grew dark and
moody. So she took the oath of the Red Lanterns who are defined by their hate and anger.
This allowed Kara access to whole bevvy of powers that Superman has never been able to access. (Although Superman has, periodically, got the powers of other Rings.)
This gross oral sludge can burn through most materials and has been described as having the force of napalm and acid mixed together.