What about supernova?
When a large star goes supernova it effectively destroys all the surrounding star systems, either by shockwave, radiation or debris. It can leave behind a cooling nebula up to a thousand light-years in diameter. The nebula and shockwave can initiate stellar fusion in gas giants and flood Oxygen rich terrestrial planets with water (Hydrogen from the nebula plus Oxygen in the atmosphere).
Betelguese is a red supergiant only a few hundred light-years away and is ready to explode in the next 100,000 years. The solar system is at risk when it does. The radiation will not be high enough to cause an extinction level event but the expanding nebula will. The expanding nebula will be thick with ionised Hydrogen gas. The Heliosphere can't stop all of it from entering the solar system. The question is how much will get in? Will it be a lot, and initiate stellar fusion in Jupiter? or a little, but still enough to flood the Earth and any terraformed planets with water. An estimated 5.5 x 1026 kg of H will reach the heliosphere. If only 280 parts per trillion reach Earth, that'll be enough to remove all Oxygen from the atmosphere. All aerobic life on Earth will be destroyed, that includes humans.
It seems terraforming planets in the solar, or surrounding systems may only be temporary, a stepping-stone that will allow us to practice terraforming before we relocate our civilisation. So when we find the right system, the right planet, we can terraform it and make it work.
I think this is a planetary nebula but it still looks awesome!