Complex sentence: Caitlin attempts to escape with the help of her doppelganger Killer Frost; however, Frost tries to murder Caitlin, forcing Zolomon to kill her in Caitlin's defense.
Split into simpler sentences: Caitlin attempts to escape with the help of Killer Frost. Frost, however, tries to murder Caitlin, leading to Zoom killing her in Caitlin's defense.