Star Trek II:The Wrath of Khan Battle in the Mutara Nebula:Spock's Sacrifice 4/8
Khan activates the Genesis Device which threatens to destroy not only himself and the Reliant but the Enterprise as well. The damaged Enterprise tries to desperately limp away from the Reliant under impulse power unable to go to warp due to the mains being offline. Spock sacrifices himself to get the Enterprise to warp to get away from the Genesis' detonation.