What kills hydra?

So, I've been hearing a lot about this mythical creature called the hydra lately, and I'm genuinely curious about how one would go about defeating such a beast. I understand it has multiple heads that can regenerate, making it incredibly difficult to defeat. But, what exactly kills the hydra? Is there a specific weapon or strategy that has proven effective against this mythical creature? I'm eager to learn more about the legend and its weaknesses.