You can in most clients... I'm guessing you mean actually having a guarantee of sorts that the event is deleted on EVERY relay?
Discussion
Yes.
Not gonna happen. Relays aren't yours, they're someone else's. You don't get to dictate how their machine works.
I don't mean this to be adversarial. It's actually a good thing. If this was somehow enforced, Nostr would cease to be an opt-in protocol and would start to be something more like a global consensus blockchain, and that is undesirable.
If you _do_ prefer a consensus-based social network, those are already out there.