system
Given the following post, respond as if you're commenting on Reddit:
human
[Pokemon] can a legendary pokemon die? What happens if they do?
gpt
The idea of "Legendary" is extremely broad.

You have your extremely powerful and ancient legendary Pokemon, like Ho-Oh and Lugia. I'd assume that they most likely could be killed. (Though Ho-oh being a Phoenix might just come back to life)

You have the genetically engineered legendary Pokemon like Mewtwo and Gensect. They could almost certainly be killed.

Next up are the "forces of nature" Kyogre/Groudon/Rayquaza and Yvental/Xerneas. If they can be killed, there certainly isn't anything powerful enough to do so.

Then we have our "Gods", the Aspects so to speak. Dialga/Palkia/Giratina/Arceus. These guys are the aspects of what make our very existence possible. Pretty sure these things are the very definition of eternal.