In the process of homebrewing, I came up with this rough outline of an ability:
As an action on your turn, you can speak words of rebuke. Creatures [in the area] must make a Constitution saving throw [against a specified DC]. On a failure, they are stunned until the end of the turn.
The primary purpose of this ability is to act as a concentration breaker – however I want to be aware of any unintended interactions such an ability can have – for example, if abilities such as Rage end on being incapacitated, however briefly, or if doing so causes a flying creature to fall.
I should point out that the ‘on your turn’ wording is there to prevent abuse including readying this action.