The following exerpt from a web-novel:
A shaft of pure actinide destruction lanced forth from its outthrust palm (...)
What does "actnide" means in this context?
I rather suspect that the author is simply misusing the word.
The actinides are the f-block elements of group 7 in the periodic table, so called because they come immediately after actinium. The elements share some characteristics, such as having largely incomplete f-shell electrons and being radioactive, but none of that is applicable here. After all, most radioactive elements aren't in the actinide grouping.
I suspect they actually meant actinic. It's another scientific term, but one that has found great currency in certain types of fiction writing, especially in the set phrase 'actinic glare'. Actinic light is usually bright and low-wavelength (blue-white).
It is most likely that the two words are related, but they mean very different things.