A (homebrew) greatsword has this feature:
Heavy Blow. [...] If you hit with this very powerful attack, the target must make a contested Athletics check. If the target loses, it is stunned until the end of its next turn.
I’m currently using an opposed roll but I’m not sure that’s the right solution. I wanted to avoid using a save DC, but want to stay within the 5e design patterns. I couldn't find much info on status effects without save DCs in the PHB.
Is there a way that 5e has done this historically? Or am I forced to use a save DC or use my own solution? I'm looking for any design conventions in D&D 5e that have inflicted a status effect without a Save DC, but also the status effect not guaranteed.