It doesn't say the sun's ray can nuke someone, it says that using a sun ray in Astarian results in a voice line. Which is probably going to be snarky based on his character and the fact that you meet him during the day and have an early conversation with him about sunlight.
The number of creatures that are affected by the spell and look like a regular humanoid in D&D is pretty low, so the first spoiler is what Astarian is and the second is that a voice line is prompted by the interaction.
You might be too thick to understand what a spoiler is since you think when something happens in the storyline impacts whether it is a spoiler, but just accept the fact that it is and some people don't like having it in post titles they cannot avoid.