At out table, I'm giving the player the stakes before they roll. They describe an intimidating action and their goal which, in this case, is to get the orc to run. I, as DM, determine that the outcome will be uncertain and tell the player what happens on a success and what happens on a failure. The success state should be somewhat related to what the player wanted their PC to accomplish. If it is something completely different b/c you, as DM, don't think their goal is possible, then you might as well say that the outcome is certain and declare that the action fails. The orc punching the fighter on a successful ability check for the fighter is... not something I would pull on a player. That is most definitely not a success.
I'm not into adjudicating by feel when it comes to rolling dice. The players deserve to know what means what before getting into situations that could be bad for their PC. If they still go for it, that's on them. If I don't give the stakes and the PC suffers b/c of how I "read" a roll result in the moment, that potentially leads to "gotcha" situations - inadvertent or otherwise.