One or more stun counters on a permanent create a single replacement effect that stops the permanent from untapping. That effect is "If a permanent with a stun counter on it would become untapped, instead remove a stun counter from it."
2025-09-19 • wotc
The stun counters don't need to be removed from the same permanent. For example, if an opponent controls three permanents that each have two stun counters on them, you could remove one stun counter from each of those permanents.
2025-09-19 • wotc
You may remove stun counters from permanents you control as well as ones your opponents control.
2025-09-19 • wotc