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.
Do a whole lot of research, then take control of the president, and pardon people for a minute. As far as I’m aware, it takes effect as long as someone hears, or I write it down or something.