Violations of the Prime Directive with Positive effects:
Star Trek Into Darkness
In the Kelvin timeline, on the planet Nibiru, a volcano was set to erupt and had it done so the natives with their homes at the base of the volcano would have been destroyed, causing the population of those natives extinction. Kirk and McCoy made several attempts to subtly lure the Nibirans away, but eventually, Spock had to place a cold fusion device in the volcano, rendering it inert and exposing the Enterprise to the natives while in the process of saving Spock from the Volcano. The ship was exposed to the natives that much is true, but a crisis was everted that would have spelled certain death for an entire civilization.
The Original Series “Miri”
On the planet of Earth-Two, the inhabitants were infected by a disease that killed adults and severely slowed the aging process of those who had not yet reached puberty. Dr. McCoy discovered a cure that was provided to the remaining children on the planet, helping them to avoid what would have been considered natural extinction.
The Next Generation “Pen Pals”
Lt. Commander Data obtained knowledge that the planet of Drema IV was experiencing extremely dangerous seismic activities. The Enterprise possessed technology that could possibly correct these disturbances. Fortunately, the Enterprise was able to neutralize the seismic activity without the planet’s inhabitants being aware of their presence, thereby saving the planet and its people with a minimal amount of interference.