Only one time use.
Think of like world leaders, celebrities, ya know 😉. Are you gonna make them do some embarassing things, or illegal acts.
My answer:
spoiler
Take control of an NSA agent with access to the most powerful hacking tools, hack everyone’s phone, install a program that randomly have a popup at random intervals, the popup message says “I’m watching you”. This also tries to spread itself to any other phone it can connect to. Pure chaos 😈
Pretty sure I can do this in a minute, depending on how good the NSA tools are.
Make the Pope announce his conversion to Buddhism (and declare it an infallible doctrine of faith, ex cathedra).
Oh that’s a good one. Get the pope to pass a bull offering everyone salvation, past, present, future, fictional, factual, human, animal, spirit.
They’d reverse it quickly, but it would be too late. It happened.
And because the Holy See has ecclesiastic jurisdiction (as we all learned in Dogma ) then it would totally count. Heaven for everyone.
And if there are angels in Wisconsin cursed by God and breaking divine infallibility unmakes the universe (it doesn’t) then the world would end.