Doctor Who
Time Lords have the power to travel in time, but they choose not to use it to change the history of other planets. The Doctor disagrees with this, because they want to use time travel to fight on the side of good against evil. However, sometimes the Time Lords give the Doctor missions to change history for them. For example, in "Genesis of the Daleks" the Time Lords send the Doctor back in time to stop Davros from creating the Daleks.