This was kind of inspired by a fanfic I saw on tumblr (can't remember the person's url or the title of said fanfic for the life of me, though) where Elsa dies and Anna becomes queen, and I wondered what it would be like if Anna had died and Elsa had to rule as queen without her sister.
"Your sister is dead... because of you," Hans told the ice queen.
Elsa, terrified at the thought that her sister, the only person she had ever loved, was dead, fell to her knees, tears streaming their way down her face. The swirling storm stopped, frozen in time. The flurries of snow hung in the air, and the wind ceased. All was silent, except for Elsa's muffled sobs.
Across the fjord, Anna stood, alive, though possibly not for long, stumbling her way to her real true love's kiss.
"Kristoff," she whispered.
"Anna," he called out back to her.
The pair forged on, trying to get to each other in time, when the sound of sword being drawn distracted Anna, and turned her attention to the one she had thought was her true love, about the kill her sister.
"Elsa." Anna ran to her sister. She knew she had to save her. "No!" She threw herself between Elsa and the sword, hoping to save her sister. Just then, the ice began to cover her, and within seconds, she was frozen solid, as if she were nothing more than an ice sculpture.
As Hans' sword connected with Anna's frozen form, it began to freeze itself, until it was cold and brittle. The sword struck the princess, and both shattered into a million pieces. Princess Anna of Arendelle was no more, just a heap of shards of ice mixed with the slivers of metal which killed her.
The clatter of the ice and metal falling to the frozen fjord caused Elsa to look up from her crying. She turned to face her broken sister behind her. Anna's face had stayed intact, and was now staring up from the mound at Elsa. She reached out to hold it, realizing this would be the last time she could ever hold her sister.
"Anna? Anna!" she muttered, as if saying the name would somehow repair her back into life. Suddenly it dawned on her. Anna was dead. But it had not been her own fault. It was Hans who had murdered her. Elsa looked up at the tall figure looming above her. "You," she said to him. "You killed her. Not me."
"So?" he sneered. "She's dead either way. What does it matter who did the deed? It's not like she'll be coming back to life any time soon. Besides, she was frozen before I struck her. You killed her first."
"No! She could have been saved! She still could have gotten her act of true love. But now she's been shattered. And that one's all on you." Elsa rose to her feet and announced to the people watching from the safety of the castle and all who could hear, "I, Queen Elsa of Arendelle, charge Prince Hans of the Southern Isles with murder, and sentence him to death!" She looked Hans in the eyes coldly. "I think it should seem fit for you to die in the same way you kill." She raised her hand and sent an icy blast at Hans' heart, just as she had done to Anna, except this time her actions were caused by malice more than fear. Hans began to turn as pale as Anna had been before her death within only seconds, as this blast had been much stronger and much more concentrated.
"No. Please. Spare me," he begged for mercy, shivering all over.
"Well, I suppose if you found your true love's kiss in time, you might live. But... Oh, Hans. If only there was someone out there who loved you," Elsa taunted. She turned and marched back to the palace gates, pausing on her way to instruct a guard. "You! Gather the shards of his sword and bring them to me. And you! When he is frozen, strike him with your sword. You saw what he did to your princess! Now do the same to him."
"But – My queen –" the soldier tried to protest.
"But what?! Would you rather be frozen with him?!" The guard frantically shook his head. "Then I suggest you do as I say, before I freeze every last one of you!" she screamed to the citizens watching. She stormed into the castle, the doors slamming behind her.
Hans was frozen before even a minute had gone by. The guard stepped forward to do his duty.
"If you can hear me, Prince Hans, I am sorry for having to execute you, but I have to say that you deserve it. You have killed our princess, and caused a great grief to settle on the people of Arendelle. Goodbye."
The sword came down on the icy prince, and his fate was sealed. Prince Hans of the Southern Isles was no more. He had made a choice, and that choice led him to his death.