Tweet of the Day: From the Palaces of St. Petersburg to Savage Mars
A character has run out of options except one. The one that if taken will surely kill them and their enemies.
This is where the character says, “I’m Taking You with Me!”
This trope is all about context. Depending on the character and the situation it can be seen as a desperate but heroic last stance, a senseless sacrifice or a final act of spite (for a villain). Of course, a skillful writer can weave all of these alternatives into one. This will be defined by the results. If the hero takes out the villain and most of their forces a top a lonely hill top fortress saving the kingdom from a thousand years of oppression, then it was worth it. But if the villain walks out enraged with little worse for ware, then it was a senseless sacrifice. And of course if the villain does it to spite the heroes that came to stop them, the it becomes a spiteful act, specially if the villains die but some, if not all of the heroes walk away.
A skillful writer can blend all three possibilities and add a few more twist to the consequences of this trope thus adding more depth to the plot.