If your chain snaps at the powerlink, do you need to replace just the powerlink? Or is the entire chain comprised?
Depends what is damaged.
Clearly the powerlink needs replacing if it broke or snapped. They tend not to just "come apart" under load but theres a small chance it never closed right.
Look at the end links in the chain, that would connect to the power link. If there is excess play in those end pins then it may be time to replace the chain.
If the chain is worn and you can feel play in all the links, then just replace it. Chains are consumables.
But if the chain seems okay then just replace the powerlink with a new one, and buy a second new spare one for your toolkit.
Powerlinks are a liability, best thing to do to do without it (get a regular link and replace on your chain) and then invest in a small and light chain tool (under 10 bucks but it's a tool you have it for all your life).
With a little practice you can open and close your chain as quickly as with your powerlink but you don't have to worry about that kind of problem.